Cannot sync contacts with android

May nextcloud server crash by Ramsonware, so I set up a new one like the old one same user accounts
uninstalled nextcloud and davx5 app on m android phone and reinstalled them.
Sync of file sand pics are working fine davx5 can connect/ is connected but contacts are not synced even if started manually without any warning or error message.
Nextcloud and apps are newest version, netcloud via web from my desktop works fine

need help hint