Please consider indicating whether both the CTRL keys are not functioning. Yet if it is only one, it might be that the problem is coming from the circuit board and you will definitely have to send it to a Repair Shop for getting it fixed.
Try another keyboard to check if there is something wrong with your OS settings.
1. If it works with the new keyboard , your keyboard is the problem.
2. If it does not work w/ the new keyboard still the same problem, OS settings in the keyboard is the problem