Unit purges, ignitor lites, burners lite and fan kicks on but burners turn off shortly after. Unit tries to start again. It goes through this 3 times then turns off unit completely. When I take the panel off and turn unit off then turn it back on, sometimes it stays on and works perfect. But once it hits the set point temp and cycles off like it should, it will not cycle back on.

Sounds like you have a dirty flame sensor. Small round metale rod that's in front of the burners-- only one wire goes to it. Clean or scrape it with a knife or steel wool. Turn power off to the system first.