When a user trys to log in and is over the number of licenses, message box pops up stating such.
 
The problem is the computer thinks DBA is open and has to be re-booted in order to re-open DBA when a seat is available.
 
Any ideas

Sometimes (usually when a system crashes) the server does not know that a user is no longer using it, and you may have two or more instances of the same user still open.
 
If you go to the Pervasive Monitor and check under Microkernal, Active Users, you can see if there are duplicates. When a user is selected it will show which files are in use by that user and it's usually pretty easy to tell which is the bogus one. If not, have that user log out of DBA and kill whichever one(s) still open.