It is sensing an obstruction or possibly excessive down force required. Check your electric eye sensors first.

Make sure your door sensors have not been bumped and that they are pointed at one another. Each one has a small light that must be on and not flickering for them to work. If you cannot get both lights to come on you may have a bad sensor or wiring leading to them.

Thanks for the directions. It ended up that one side were the plastic sensor was lose and hanging down preventing a clear line to the other side. Just straigthened and tightened wing nut. Perfect.