Ok, not clearing properly and now no signature found. It would appear you have one of the following issues.
*Dead or low battery on controller card
*Corrosion on the controller card- not making good connection
*Bad controller card
*Corrupt boot chip on controller card
*Bent pin on backplane or controller card
*Bad ribbon cable (i.e, broken wire or bare wire shorting)
I would inspect the ribbon, headers and pins first especially if it is an SAVP/SMLD... lots of sharp edges. Smallest fray in the ribbon can cause major issues.
You did confirm the doors are reporting as open correct? Those are controlled by the controller card also. If they cycle all open/all close it typically indicates a short. But for sure Logic and Main doors need to be open throughout the clearing process.
If you have another working machine to test each of these components in that would be ideal but visual inspection goes a long ways. In the event it is a bad card, ribbon etc. many vendors and members on here along with myself have these parts available pretty cheap.
Keep us informed and good luck.
D