This is a very old garage door opener. Brand name is "Auto Mate". It is
probably 25 years old or even more. It was working fine until last week.
There was a paint bucket which stopped the door while it was closing. After
that I am unable to close the door. Every time I activate the door, it
opens, but it will not reverse direction.

Before you ask, this door does not have an optical sensor for obstructions.

Any suggestions would be appreciated.