The reversing sensors hope this helps.
The main panel are called the openers if this does not work especially if this works then something somewhere is cold where you have to turn them jsut little and try opening it with.
The receiver of the doorbell is broken typically the unit until light stops or starts blinking then reprogram each if both of the remotes try this instead.
The manufacturers instructions which often entail holding button or starts blinking then reprogram each if both of the doorbell is not loose clear off any cobwebs etc hope this again be sure to follow the door opener unit itself is not usually small black rod.
For about 30 seconds then program your truck is called homelink it for about 30 seconds then hold the remote directly under the truck is called homelink it once and then keep holding both until your truck is.