Goto location:
/usr/sap/SID/JXX/j2ee/cluster/server0/logs.
here you will find the error logs in default trace and application logs.
Anyway, to configure UME from configtool use below parameters.
If your JAVA stack is UP and running then you can goto useradmin and configure UME.
However, when access to UME is denied JAVA won't start as core UME service is halted(check dev_server0 and std_server.our for error on this.)
Divyanshu