Thanks, everyone! Before I tried to take the magnet off, I moved it around every way I could, and it finally started working again. The end of it is angled in a bit and it works now. Apparently it is just barely close enough and the end has to be tilted in toward the spokes.
The sensor is tied very tightly to the fork so I don't think that I can slide it toward the hub any. Now that I know how the magnet has to be positioned, I'll try to remember to check that. I appreciate your help.