Keyless Entry/unlocking - Fob Off

[Skullb]

My key works fine once in the car.
The central locking switch on the dash works .
The remote from the key fob will not lock/unlock the car and the front and rear boots buttons also do nothing. The LED's do flash but nothing unlocks.
This key fob has worked fine until about 10 days ago. I have put a new battery cell in and it flashes on all buttons.

On the top of the dashboard in car the Alarm LED is not flashing at all. ( it should flash 5 times per second for radio signal reception and every 2 secs when the car is locked and alarm on.
Preumably this means the keyless entry Antenna is not working .

Any suggestions please ?