I am using ICSx5 V. 1.8.6 on a Sony E2303 (Aqua) with Android 6.0.1(German language version). Yes, this is outdated, but it worked fine until 4 weeks ago. Now it stopped syncing both my calendar subscriptions (one is an ics with login credentials, one a url to a shared webcalendar).
I have not changed anything to the setup on purpose and followed the threads here regarding that issue. ICSx5 is exempted from battery optimization. But even a manual sync from the calendar app does nothing.
The app is not stored on the SD card, actually it is not possible with that Android version to move it to SD. I deinstalled and reinstalled the app from F-Droid without success. The subscribed calendars are correctly recognized, but the status in ICSx5 remains at “not yet synchronized” (i.e. “noch nicht übertragen”) for ever.
Any leads what could be wrong are appreciated. Thanks a lot