Chamberlin Liftmaster Professional (CB24 & dual LYN400.24v)

[Tussun]

Hi, I have just installed the la400 gate openers and can't get them to work! I have error code (7 red blinks) which is issue with photocells, have checked alignment and wiring but no joy. Decided to disconnect then in the hope that I could then test the gates worked but the only way I can get the arms moving is during the setup stage when you press all 3 buttons and then sort the travel distance, after that nothing, remotes don't work even though programmed!

1. Can gates work with out photocells?
2. If error with photocells does it shut down the circuit board so gates won't work?

Any help would be great

Carl