Yamaha DTXpress/DTXplorer/DTXtreme

It's probably too late to help your gig, but you can swap inputs 1 & 9.  You don't say which model DTXpress it is, but in the DTXpress III manual it is in the reference manual page 15 - section 2.3 "Input Exchange".  That should allow you to use input 9 for your kick without having to reprogram all the kits.

It is possible for a module input to fail - just a bad connection on the connector in the module could do it - but I haven't heard of it happening.  I don't know if it is possible that you have accidentally changed something, or the module settings have become corrupted, but it is worthwhile checking the trigger settings: pad type, MVEL, GAIN.  Also, check the attenuator switch on the back of the module.  Even check you haven't already got a 1 to 9 input swap.  In trigger edit mode see if you are getting a display when you hit the pad, even if there is no sound.  Check rejection settings look sensible (although I don't think you can adjust them far enough to stop it working).

Keith.