Reprogramming a Cobra Key Fob on a Chimaera

[Delory]

Hi all,
I know this has been covered before, but I can't find the answer I need in the previous questions. I recently purchased a 7777 Cobra key fob to use with my 99 Chimaera - I presume many other TVRs use the same type) and need to program it to work with the existing system by entering the pin code. I followed all the instructions in the Cobra handbook meticulously:-

1. Turn the ignition ON and OFF 3 times within 7 seconds, the system LED will illuminate
2. When the LED extinguishes switch the ignition ON
3. The LED will flash. Count the number of flashes to correspond with the first digit of the PIN code

All good so far.

4. Switch the ignition OFF then back ON and count the flashes for the second digit of the PIN code

Here's the problem. After entering the first digit, and turning the ignition off and on to enter the second digit, the light does not flash, and I can enter no more digits. I have tried a hundred times but can not enter the second digit.

Has anyone ever encountered this problem?