Thanks for looking into this problem.
So I found this forum post.
It had a project that lets me play agogo on my machine. ( I stripped it down to just agogo)
Agogo.dorico (493.7 KB)
The post says I need to export the percussion map and import it to any project I want to use it in. I did that, and it now shows agogo as one of the instruments of Yamaha XG copy (the imported map).
(Oddly, the original Yamaha XG is missing the agogo. It has MIDI …65, 66, then 69, 70…)
I restarted Dorico, but No Agogo still does not play agogo.
Any suggestions? Do I need to activate the new percussion map somehow?