Discovery roomba not turning on

Question

Two days ago my Discovery Roomba would not turn off, so I let it run until the battery went dead ( over 1 hour). Then I put it back on the charger and it seemed to charge like normal . Yesterday I went to use it and it would not turn on. I don't think there is a problem with the battery as it is only a couple of months old and did fine the last time it was used. Any suggestions? Thanks, Cindy