The question was not related to multi-user at all.
As Microsoft recommends, I have a standard user account separated from an account with administrator privileges.
Anyway, the workaround that you suggested is working.
I have temporarily added my standard user account to the Administrators group, have installed Ultimate S Pro again.
Then removed my std user account from Administrators.
Everything works as intended. Thank you!
It would be very nice, if you had documented this procedure in the readme file.