Back to basics... what changed just before it stopped working... what did you touch related to treasure chamber as part of the refurb?
Mpu... not likely cause, other stuff would likely not be working.
New driver board... not likely if kicker does work sometime...
In the hole switch... no because something registers...
What else was changed or fixed?
Wiring ? Connectors? Proms? Leaf switches? Kicker hole assembly? Was it working before the refurb or did you buy it not working?
When you trigger the treasure chamber is it registering the correct thing? Ie. 5x when the drop targets are down, then free ball... do the drop downs pop up again after free ball? Will you get a special after you knock down drop targets again and activate saucer?
In your first post you said it makes sounds and scores points... Im not sure it's supposed to do that... 5x, free ball, special when valley of demons drop targets are down first... is what it should do... unless you get some points in addition; I'll check mine. Did you accidentally rewire it to either that small top bumper or the golden cliffs? If you press the top bumper on left beside golden cliffs does it cause the treasure chamber kicker to work?
added pictures where the small bumper is... if you've wired incorrectly to this switch signal, all you would get is a small "bing!" and maybe 100 or 500 points. It's really close to the Treasure Chamber so is it possible you swapped the wires?
paragon top bumper 2 (resized).JPG
paragon top bumper_LI (resized).jpg