Cannot get pipelight to appear in the list of plugins in firefox

I am running Fedora 22. I have tried installing pipelight using the rpms from rpmfusion and using the fedora 21 rpms as described on the pipelight site. Either way I get the same issue.

I have got to the point where "pipelight-plugin --system-check" is returning passed for all sections. I have silverlight or silverlight5.0 installed. However when I start firefox pipelight does not appear in the list of plugins, silverlight test pages say install silverlight and the pipelight diagnostics page doesn't see pipelight being installed. I get the same in Konqueror.

I have tried deleting ~/.wine-pipelight, running "pipelight-plugin --create-mozilla-plugins" and when I start firefox I get dialogs about installing pipelight, then silverlight, but it still doesn't work. Doing this and running firefox from the command line I get:

[PIPELIGHT:LIN:unknown] attached to process.
[PIPELIGHT:LIN:unknown] checking environment variable PIPELIGHT_SILVERLIGHT5_1_CONFIG.
[PIPELIGHT:LIN:unknown] searching for config file pipelight-silverlight5.1.
[PIPELIGHT:LIN:unknown] trying to load config file from '/home/elwe/.config/pipelight-silverlight5.1'.
[PIPELIGHT:LIN:unknown] trying to load config file from '/etc/pipelight-silverlight5.1'.
[PIPELIGHT:LIN:unknown] trying to load config file from '/usr/share/pipelight/configs/pipelight-silverlight5.1'.
[PIPELIGHT:LIN:unknown] sandbox not found or not installed!
[PIPELIGHT:LIN:silverlight5.1] using wine prefix directory /home/elwe/.wine-pipelight.
[PIPELIGHT:LIN:silverlight5.1] checking plugin installation - this might take some time.
[install-dependency] Downloading and running wine-silverlight5.1-installer.
Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
fixme:winediag:start_process Wine Staging 1.7.51 is a testing version containing experimental patches.
fixme:winediag:start_process Please report bugs at http://bugs.wine-staging.com (instead of winehq.org).
wine: cannot find L"C:\\windows\\system32\\winemenubuilder.exe"
err:wineboot:ProcessRunKeys Error running cmd L"C:\\windows\\system32\\winemenubuilder.exe -a -r" (2)
fixme:ole:RemUnknown_QueryInterface No interface for iid {00000019-0000-0000-c000-000000000046}
Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
[PIPELIGHT:LIN:silverlight5.1] basicplugin.c:299:checkPluginInstallation(): Plugin installer did not run correctly (error occured).
[PIPELIGHT:LIN:silverlight5.1] basicplugin.c:116:attach(): plugin not correctly installed - aborting.
[install-dependency] Downloading and running wine-mpg2splt-installer.
/tmp/pipelight-wine-mpg2splt-installer.cab: WARNING; possible 6872 extra bytes at end of file.
Extracting cabinet: /tmp/pipelight-wine-mpg2splt-installer.cab
  extracting /home/elwe/.wine-pipelight/drive_c/windows/system32/mpg2splt.ax

All done, no errors.
regsvr32: Successfully registered DLL 'mpg2splt.ax'

So it looks like the plugin didn't install correctly. If I enable silverlight 5.0 instead I get the same, with different version numbers.