Thanks! I’ll check the drain lines. I assume you mean the two that empty into the floor drain?

As to the blink light codes, I’m seeing 21 green blinks to one red blink

I don’t see this sequence mentioned in the manual or furnace stickers (maybe it’s an “ all OK” code).

I do find things like this online:

https://www.justanswer.com/hvac/679ui-trane-xv95-green-light-blinks-21-times-red.html