Error "Enter a sales area"

Hello,

While I am trying assign user to employee The error appears "Enter a sales area"

The problem started while I was trying create a service order. I received error "User XXX (Employee responsible) is not a business partner". I think the root cause is missing assignment --> user to employee. When I am trying to do that,  the error "Enter a sales area" appears.

Could you please help with solving the issue ?

Thank you in advance.