Login at Kopano WebApp fails for only one user

Hi all, I have a problem with one user unable to login to Kopano WebApp. The same user can login to univention console without error. All other users are able to login to WebApp.
Config: UCS as Member of AD with Kerberos authentication. Not using Samba.
How to find solution?
Thanks in advance

Found Solution inhttps://www.cubewerk.de/2022/10/25/univention-adsearch-kinit-password-incorrect-failed-to-bind-ldap-client-internal-error-nt_status_unsuccessful/
There was a broken join to active directory. Solution was setting password for UCS machine at windows server to the machine password.