I’m running the CardDAV server locally, with no internet access, on a Synology NAS. The phone and account have no trouble connecting, no error syncing. It all worked seamlessly on Android 7, but just stopped working on Android 8. I have deleted the app and reinstalled (apk from f-droid) multiple times. I also have reset the contacts app many times as well. Attaching the debug file, since the verbose logging doesn’t work for me (used to work also). The phone is a CAT S41. For now, the only app to work was “ContactSync”, but as the full version is paid, it is not a long term solution.