I'd running google play "paid" davdroid running for some weeks for cal/card against my owncloud server without any problems.
Some days ago "google play updated" (okay I had allowed it to version 0.4-alpha. Directly after that update it did not syncronize anymore.
It don't give any error, it's just keep the last sync time before that update and it won't pull or push any changes whether to cal nor card.
I have used it on a Xperia Z and a Galaxy Note both running a custom ROM, with no changes over the last days.
Any idea what change form 0.3x to 0.4 could cause this behaviour?
---- some further testing ---
Deleting the former working davdroid account and the URL on my Galaxy Note and trying to recreate a new account will give "E/A Fehler: Cannot verify hostname: 192.168.100.1