Cannot get iOS to sync calendar

Hey everyone,

I have tried for two hours now, but i just cannot get the IPhone 13 of the bwoa (best wife of all) to sync the calendar via caldav.
I am just trying around on the lan so I don’t use ssl. My server address for caldav on iOS is

In entered this, the username and the password but always get an error “CalDAV-Accountüberprüfung fehlgeschlagen” (“CalDav account checking failed”)

Syncing my android devices and the laptops was absolutely straightforward and installing the nextcloud app on iOS also worked fine. I found some articles concerning ssl on the newer versions of ios online, but nothing about this error without ssl.

Does anyone know how to get this working?

Greetings + Thanks


EDIT: Added the inof that installing the nextcloud app worked fine