How can I fix this garage door opener?
When I was working on modifying my garage door opener, I found two things:


One of the failure sensors was tripped; there are several, but the one that got me was the obstruction sensor. It was incredibly easy to bypass by short-circuiting the sensor's connection with a jumper wire.
The communication may be off, especially since you replaced the board and remotes sometimes don't clear their memory so well; check the blink patterns in the diagnosis manual. The blinks may indicate that the remote's rolling keycode pattern is incorrect. This is exactly what happened to me.