I have a garage door opener that will not put the door down. Help

My garage door opener will not put the door down, I have cleaned the eyes on it , did'nt help. It will come to the bend to come down but then it goes back to start and that's it... Thanks

If there is no obstruction, or damaged wheel that is blocking it in the tracks, the possibilities beyond that depends on how it works. They don't all work the same.