Thanks to those who helped. I went out and reversed the diode today, and it
worked perfectly the first time.
I think it is a diode rather than a resistor because it only has one silver
color band on it, and IIRC, resistors have at least two color bands. The
length of the "barrel" part is only about its diameter.
Anyway, if the polarity of the component was the problem, reversing it fixed
it. If it just wasn't getting contact, then redoing it made contact. The
question of polarity is not relative once it works. I didn't want to double
test it, because I learned that when you get it working, LEAVE IT ALONE.
A veterinarian friend of mine said something that they told him in vet
school. "Better is the enemy of good. If you've done something of a good
quality, leave it alone, and don't try to make it better."
Anyway, "Be it ever so humble, there's no place like home" now plays start
to finish with one jab on the new door bell bar.