Currently, new DAVdroid versions uploaded to Play Store are refused because “they violate Google’s payment policy”:
Thanks for submitting your app to Google Play. I reviewed DAVdroid – CalDAV/CardDAV Sync, at.bitfire.davdroid, and had to reject it because it violates our payments policy. If you submitted an update, the previous version of your app is still live on Google Play.
Unfortunately, we don’t have any idea why the payment policy is said to be violated. We have removed the donation link from the Google Play variant of DAVdroid and submitted it again, but they have refused it again (payment policy violated).
So, at the moment, we can’t update DAVdroid on Play Store and don’t even know why. We have contacted Google and hope that this problem can be resolved soon.