Dear Kasata,
whe you copy the user the roles will be copied to the new user, not the profiles. SAP the tries to assign profiles based on the copied roles and, in you case, fails.
You acn check if profiles from the model user are all assigned. Probably there are some roles where the associated profiles are not assigned.
Just to help you understand whats going on, you still have to follow the advise of Alex and Julius.
greetings
Alexander