I have a similar problem on my Oneplus 3 with OxygenOS 4.0.3 (Android 7.0). My settings are to auto sync every hour (I’ve also changed this to 15 min for testing purposes) and immediately after local changes to my Nextcloud server. This does not work, the only way to sync is if I run it manually.
I’ve checked the battery optimization setting and DAVDroid app is set to NO optimization.
Also the permissions look fine:
I’ve cheked the log but there is nothing in it until I do the manual sync:
Here is also my debug info:
EDIT: Just to add that sync is also not working the other way around: if I change something on the Nextcloud server the changes are not synced to my phone unless I do manual sync in the DAVDroid.
Is there anything else I could check to get the sync done?