Kenmore Elite - won't drain - drain pump not activating

I have a Kenmore Elite from 2005 which has been working like a champ for the past 10 years. Every 1-2 years I have cleaned out the sump trap and chopper assembly. I just decided to do that last week again, and when I put everything back together, it ran fine with a vinegar full cycle rinse. Now, at then end of a cycle, it won’t drain from the bottom of the basin, all I hear is a click behind the loading door, like a relay activating type of sound, but no pump or motor sound whatsoever. And just to be clear, it fills fine, it goes through the cycle progress fine, the pump for recirculating the water and spraying through all ports is working fine. It’s just dead silent after the "click" when the drain is activated. On this model there is a "Cancel/Drain" button to abort a cycle. When I try that button, I get the same behavior - click behind the control panel in the door and crickets after that.

I’m wondering what possible components may be bad. Is there a relay that I can check with my meter? Is power getting to the drain pump, and how can I check for that. Is there a timer in this unit that could have gone bad? Or is the Electronic Control Board bad, and how can I check for that? I’m trying to avoid trial-and-error repair, where I replace parts that aren’t broken until I discover which one was bad. Thanks - Ben