Diagnosis
You made the business area a required entry field in the screen layoutcontrol or you want business area balance sheets in company code &V1&.Therefore, every asset has to be explicitly assigned to a businessarea.
You did not specify a business area.

System Response
The asset cannot be saved without a business area.

Procedure
Enter the business area or another additional account assignment (suchas cost center, responsible cost center, internal order or maintenanceorder) from which the business area could be determined.