Nextcloud 12 does not support IOS

I have just migrated from owncloud to nextcloud latest version. Thunderbird-calender/contacts sync. works fine, But I can’t connect any longer calender or contacts from IPad/IPhone to nextcloud nor works the nexcloud app on my IPhone.
Any solution for this?

Solved all problems with IOS for the time being. Now Nextcloud synchronizes 2 IPhones, 2 IPads, 3 Windows-10-Desktop-PCs and 1 Windows 10-Laptop (Files, Contacts and calender)
However, although it works now very satisfying some open issues are left

  1. Not my official geotrust domain certificate is delivered to the IOS-devices but the server certificate. Not sure whether this belongs to nextcloud or not.
  2. It should be mentioned in the installation docs, that it takes some time until the freshly installed new calender account appears as calender on an IPhone/IPad. I discovered it by chance because I left the room after the installation of a caldav-nextcloud-calender supposed it was succesless but saw the calender working when I returned 30 min later.
  3. ssl-seems to be an issue what works not very stable. After 6 attemps the installation of caldav-calender and its connection to nextcloud worked but it was the same procedure which failed 5 times and succeeded at the six attempt. Not sure whether it is a generell server matter or belongs to nextcloud.

If I will find some time after Christmas I will check the relevant protocolls of my server to try to find out something more precise and will post it