You may need to install the OBDLink drivers. Does the LED on the interface light up red or yellow when you connect it to the computer? Red means drivers not installed. Yellow means everything's fine, ready to connect to the car.
Is this the first time you're using FORScan, OP? If yes, then you either have an issue with the software, or have an incompatible OBD2 cable. If not, then most likely your temporary (2-month) license expired. In that case, just download a new one. Good luck.