Second 4450 on 4424 set does not light up

[thephonelady]

I have a customer with a 4424 set with 2 4450 modules and the second one does not light up all of a sudden. I tried swapping them and they both work ok as adjunct 1 and the cords are ok. The second one can be used for calling the users but does not light up. Any ideas? I did not have another power supply to test with.
Thanks in advance

 

[Evco]

Did you recently upgrade to R7? R7 no longer works the lights correctly on the 4450 units.

 

[thephonelady]

Evco- No this is an older 406 and only 1 of the units does not light and the other works fine all the time.