Replace RWB2 Programmer with Select 207XL - No Boiler FireUp

I have just replaced a Landis & Gyr RWB2 programmer with a Select 207XL. After fitting, my Baxi back boiler does not fire up.
When I put the RWB2 back in place all is OK.

On the back plate, which I have not disturbed, there are connections to pins N, L, 3 and 4. The middle pins, 1 and 2, are unused.

Any ideas anyone?
Dave

Sounds like you have a duffer. Does the display and indicators work? Sometimes it can be difficult to seat it on the backplate properly.

Buy a Honeywell ST9400C next time, light years ahead of the Sunvic. £15 more though.

Thanks Simon - Display appears to be OK compared with the user instructions and all appeared OK during the programming exercise.
I'll try re-seating it per your recommendation and try the Honeywell if all else fails.
Dave