i looked into the log fie there is a few errors in there.
the last 7 entries are
system eror 13: permission denied
sys_auth: execve failes for /opt/psa/admin/sbin/sys_auth: permission denied.
so i changed owner from root to psaadm and now i guess i am a step further.
now its telling me when i try to logon to plesk cp:
Error: You have entered incorrect username or password.
but i am sure i enterd userid root and the right password.
the strange thing is, i have a second test plesk server which i updated one week before this one, there the update worked fine and i have no problems, and if i compare permissiones, the files there are all owned by root, like this server before i changed owner to psaadm, on the other server this is no problem, so why here?