Edbuet

Hello there i recently bought a 2007 inpreza wrx and the key fob had been working fine but over the past few days i would need to press the button a few times to lock/unlock and now it has completley stopped working, when i unlock the car with the key the immobiliser kicks in and i cannot start the car and the immobiliser code doesnt seem to work at all, a fob repair man looked at it and said he couldnt tell exactly what the problem has anyone experienced this problem before? Thank you