garage door -new thread

Thanks for earlier responses. The title "Garage door" seems to have been used a lot so I'm trying to retitle to avoid excessively long thread.
The hardwired button works if held in. The yellow light on the back (1/2HP Craftsman) flashes 2 every few seconds. The sensors have no lights. I disconnect the green light sensors and wired it directly to the back of the unit. If working correctly, I should see a light but since not lined up, it should flash. I see no light. I'm convinced either the main box has a logic board failure of the sensors are bad. Is there anyway to determine where the problem might lie without trial/error? Also, if parts of the unit need to be replaced, would it be better just to replace all? The unit is approx. 5 years old.
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