Wayne Dalton automatic garage door wont close fully?

Wayne Dalton Comfort 220 - automatic door opener.

We had a burst pipe last night which flooded through the garage ceiling and into the door operator. I opened the door by pulling the red cord. I think it's dried out now... I've pressed the red button back, the door has engaged the chain but it closes fully then raises up about six inches from the ground before stopping. My installer is on holiday till 26/07 can anyone advise please? Easy instructions, I'm a blonde!!