iOS Notes App Login

Hello, I am running Nextcloud in 2 self-hosted instances and since last week in a Managed Nextcloud by Ionos.
With all instances there is a problem connecting the official iOS Notes app to an account, no matter which instance I’m trying to connect to.
iOS App is version 4.2.0
self-hosted instances are Nextcloud 28.0.1
Ionos Nextcloud is 27.1.5
The steps:

  1. starting in the iOS app and connecting iOS App to Server with “Login”
  2. authenticate via
    a) Nextcloud-credentials + 2FA or
    b) App-Token
  3. “grant access”
  4. back in the iOS App the “Login”-Button is still visible and there’s no connection eg. sync with notes in the instances

Any idea for a solution?