I have the same problem.
1. Two iPhones X, running OS 12.2
2. iOS is running Enpass 6.0.6 (234). Windows Desktop is running the latest Enpass version.
4. No error messages. As mentioned by the OP, the sync works fine, except it does not sync automatically, behind the scene, as soon as any change is detected. I have to open Enpass on iPhone and wait for like 10-15 seconds for Enpass to sense that it needs to start syncing and then the sync circle starts and the sync is done. Most of the time when I am on a website, trying to enter the password and that automatically takes me to Enpass, it will not find the entry for website on enpass, because the sync was not done previously.
5. Yes the date and time setting is automatic on all devices.