Check where you can serve the Greek FIR with your services
At certain airports FRA’s (Facility Rating Assignments) are in effect. This means that on certain Airports ATC must have a specific rating in order to be allowed to take a position. Example of a FRA could be: “The xxxx_APP position may only be taken by Advanced ATC Trainee or higher.” This means that if you have the rating of ATC Trainee you are allowed to log-in as _DEL, _GND and _TWR on that particular Airport, you are however not allowed to log-in as _APP and _CTR.
If you are looking for FRA restrictions and you have the Guest Controller Approval be sure to check the GCA menu