How do I write data to a Type2 tag?

I'm struggling writing data to a Type2 tag (KAMOR NFC TAG 203)... Please help!!!

Here is the snippet of code I'm using:

import nfc

def connected(tag):
  print tag
  if tag.is_present:
    print "Tag is present"
    s = bytearray(b"HHHH")
    tag.write(0,s)
    print "Data written to tag"
    print s

clf = nfc.ContactlessFrontend('tty:AMA0:pn53x')
print(clf)
clf.connect(rdwr={'on-connect': connected})

Am I missing something? Do I need to format the tag? I'm using a similar code to read it and it always return the same value...

Thanks in advance!