Unable to start scan on HP LaserJet Pro M29w

I'm using Ubuntu 18.04 and the HP LaserJet Pro MFP M29w printer/scanner. I downloaded and installed HPLIP and set up the printer, which works great for printing.
But the scanner does not work. Using simpe-scan, I get an error: "Unable to start scan". This happens either via wifi or USB. I can see the scanner arm moving, but get no output of the scan, and I always get that same error.
Output from "simple-scan -d": WARNING: scanner.vala:1224: Unable to start device: Error during device I/O
When using the xsane, I get: Failed to start scanner: Error during device I/O

dusan@hp:~$ sudo hp-check -t
ERROR: ld.so: object 'libgtk3-nocsd.so.0' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
[sudo] password for dusan:
Saving output in log file: /home/dusan/hp-check.log

HP Linux Imaging and Printing System (ver. 3.19.5)
Dependency/Version Check Utility ver. 15.1

Copyright (c) 2001-18 HP Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Note: hp-check can be run in three modes:
1. Compile-time check mode (-c or --compile): Use this mode before compiling the HPLIP supplied tarball (.tar.gz or .run) to determine if the proper dependencies are installed to successfully compile HPLIP.
2. Run-time check mode (-r or --run): Use this mode to determine if a distro supplied package (.deb, .rpm, etc) or an already built HPLIP supplied tarball has the proper dependencies installed to successfully run.
3. Both compile- and run-time check mode (-b or --both) (Default): This mode will check both of the above cases (both compile- and run-time dependencies).

Check types:
a. EXTERNALDEP - External Dependencies
b. GENERALDEP - General Dependencies (required both at compile and run time)
c. COMPILEDEP - Compile time Dependencies
d. [All are run-time checks]
PYEXT SCANCONF QUEUES PERMISSION

Status Types:
    OK
    MISSING - Missing Dependency or Permission or Plug-in
    INCOMPAT - Incompatible dependency-version or Plugin-version

-Gtk-Message: 08:42:19.502: Failed to load module "canberra-gtk-module"

---------------
| SYSTEM INFO |
---------------

 Kernel: 4.18.0-21-generic #22~18.04.1-Ubuntu SMP Thu May 16 15:07:19 UTC 2019 GNU/Linux
 Host: hp
 Proc: 4.18.0-21-generic #22~18.04.1-Ubuntu SMP Thu May 16 15:07:19 UTC 2019 GNU/Linux
 Distribution: 12 18.04
 Bitness: 64 bit

-----------------------
| HPLIP CONFIGURATION |
-----------------------

HPLIP-Version: HPLIP 3.19.5
HPLIP-Home: /usr/share/hplip
HPLIP-Installation: Auto installation is supported for ubuntu distro 18.04 version

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.19.5

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/HP
ppdbase=/usr/share/ppd
doc=/usr/share/doc/hplip-3.19.5
html=/usr/share/doc/hplip-3.19.5
icon=/usr/share/applications
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv/hp
bin=/usr/bin
apparmor=/etc/apparmor.d
# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=no
foomatic-drv-install=no
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.19.5
restricted-build=no
ui-toolkit=qt4
qt3=no
qt4=yes
qt5=no
policy-kit=no
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no
apparmor_build=yes
class-driver=no

Current contents of '/var/lib/hp/hplip.state' file:
[plugin]
installed = 1
eula = 1
version = 3.19.5

Current contents of '~/.hplip/hplip.conf' file:
[upgrade]
notify_upgrade = false
last_upgraded_time = 1560197929
pending_upgrade_time = 0
latest_available_version = 3.17.10

[last_used]
device_uri = hp:/net/HP_LaserJet_MFP_M28-M31?hostname=NPI0240A5.local
printer_name =
working_dir = .

[settings]
systray_visible = 0
systray_messages = 0

[commands]
scan = /usr/bin/xsane -V %SANE_URI%

[refresh]
rate = 30
enable = false
type = 1

[polling]
enable = false
interval = 5
device_list =

[fax]
voice_phone =
email_address =

[installation]
date_time = 06/11/19 08:40:58
version = 3.19.5

 <Package-name> <Package-Desc> <Required/Optional> <Min-Version> <Installed-Version> <Status> <Comment>

-------------------------
| External Dependencies |
-------------------------

 cups CUPS - Common Unix Printing System REQUIRED 1.1 2.2.7 OK 'CUPS Scheduler is running'
 gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.26 OK -
Gtk-Message: 08:42:21.747: Failed to load module "canberra-gtk-module"
Gtk-Message: 08:42:21.774: Failed to load module "canberra-gtk-module"
 xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.999 OK -
 scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.27 OK -
 dbus DBus - Message bus system REQUIRED - 1.12.2 OK -
 policykit PolicyKit - Administrative policy framework OPTIONAL - 0.105 OK -
 network network -wget OPTIONAL - 1.19.4 OK -
 avahi-utils avahi-utils OPTIONAL - 0.7 OK -

------------------------
| General Dependencies |
------------------------

 libjpeg libjpeg - JPEG library REQUIRED - - OK -
 cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - 2.2.7 OK -
 cups-image CUPS image - CUPS image development files REQUIRED - 2.2.7 OK -
 libpthread libpthread - POSIX threads library REQUIRED - b'2.27' OK -
 libusb libusb - USB library REQUIRED - 1.0 OK -
 sane SANE - Scanning library REQUIRED - - OK -
 sane-devel SANE - Scanning library development files REQUIRED - - OK -
 libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.7.3 OK -
 libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.1.1 OK -
 python3X Python 2.2 or greater - Python programming language REQUIRED 2.2 3.6.8 OK -
 python3-notify2 Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
 python3-pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 OPTIONAL 4.0 4.12.1 OK -
 python3-pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 4.12.1 OK -
 python3-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.2.6 OK -
 python3-xml Python XML libraries REQUIRED - 2.2.5 OK -
 python3-devel Python devel - Python development files REQUIRED 2.2 3.6.8 OK -
 python3-pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 1.1.7 OK -
 python3-reportlab Reportlab - PDF library for Python OPTIONAL 2.0 3.4.0 OK -

--------------
| COMPILEDEP |
--------------

 libtool libtool - Library building support services REQUIRED - 2.4.6 OK -
 gcc gcc - GNU Project C and C++ Compiler REQUIRED - 7.4.0 OK -
 make make - GNU make utility to maintain groups of programs REQUIRED 3.0 4.1 OK -

---------------------
| Python Extentions |
---------------------

 cupsext CUPS-Extension REQUIRED - 3.19.5 OK -
 hpmudext IO-Extension REQUIRED - 3.19.5 OK -

----------------------
| Scan Configuration |
----------------------

 hpaio HPLIP-SANE-Backend REQUIRED - 3.19.5 OK 'hpaio found in /etc/sane.d/dll.conf'
 scanext Scan-SANE-Extension REQUIRED - 3.19.5 OK -

------------------------------
| DISCOVERED SCANNER DEVICES |
------------------------------

device `hpaio:/net/HP_LaserJet_MFP_M28-M31?hostname=NPI0240A5.local' is a Hewlett-Packard HP_LaserJet_MFP_M28-M31 all-in-one
device `hpaio:/net/hp_laserjet_mfp_m28-m31?ip=192.168.1.219&queue=false' is a Hewlett-Packard hp_laserjet_mfp_m28-m31 all-in-one
device `hpaio:/net/officejet_4650_series?ip=192.168.1.254&queue=false' is a Hewlett-Packard officejet_4650_series all-in-one
device `hpaio:/net/HP_LaserJet_MFP_M28-M31?hostname=NPI0240A5.local' is a Hewlett-Packard HP_LaserJet_MFP_M28-M31 all-in-one
device `hpaio:/net/hp_laserjet_mfp_m28-m31?ip=192.168.1.219&queue=false' is a Hewlett-Packard hp_laserjet_mfp_m28-m31 all-in-one
device `hpaio:/net/officejet_4650_series?ip=192.168.1.254&queue=false' is a Hewlett-Packard officejet_4650_series all-in-one

--------------------------
| DISCOVERED USB DEVICES |
--------------------------

No devices found.

---------------------------------
| INSTALLED CUPS PRINTER QUEUES |
---------------------------------

HP_LaserJet_MFP_M29w_0240A5_
----------------------------
Type: Printer
Device URI: hp:/net/HP_LaserJet_MFP_M28-M31?hostname=NPI0240A5.local
PPD: /etc/cups/ppd/HP_LaserJet_MFP_M29w_0240A5_.ppd
PPD Description: HP LaserJet MFP M28-M31, driverless, cups-filters 1.20.2
Printer status: printer HP_LaserJet_MFP_M29w_0240A5_ is idle. enabled since Tue 11 Jun 2019 08:40:11 AM EDT
Communication status: Good

--------------
| PERMISSION |
--------------

No errors or warnings.

Done.