I can’t find the post in any searches, but I recall seeing recently that the lap counter for the Volcano Circuit has been disabled during the Tour of Watopia. It may be that disabling the lap counter had the unintended consequence of also disabling the associated achievements.
Zwift could be more transparent in this regard.
Edit -
I found the post:
https://forums.zwift.com/t/volcano-circuit-lap-counter-not-working/64293/17