Yamaha DTXpress/DTXplorer/DTXtreme

It has been a long time since I tried to do any midi sequencing with 
my drum kit. Now I have a problem.

I am able to get the pads to send MIDI, but I can not get them to 
respond to MIDI. The synth section of the drum brain works fine, but 
I can not get the drum sounds to work on channel 10.

I know if I re-set factory settings it will work, but I don't want to 
do that because I have a lot of custom drum kits that I want to keep.

This has worked before. I don't know what to do. I have been over 
every damn setting I can find. What do I need to do to make sure I 
can get the brain to play back MIDI drum notes??

Alex