I just got a glass bed in for my printer and have tried unsuccessfully for over an hour now trying to get it to auto level with different shades of white printer paper and cardstock.

Is there a sensor that I need to look at or a photoresistor that needs cleaned or replaced?

If I take the glass off, it auto levels fine, usually. The exception is when I've been printing for awhile and the original plate has gotten a bit shiny. I solve that by buffing it with some 000# steel wool...

Help, please?