Have a few keys that do not work on my Yamaha DGX205

by Darla
(Pocola Ok)

There are the 3 lower E's and the 2 lower Bb's that wont play. I cleaned off any dust and even looked under the green board. There was a small amount of dust that I took off with a paint brush. Put it back together and still nothing. What else could it be? All the connectors look good, but I am no expert.