Sims can't join the yoga class at the spa; ANY spa lot.

This bug is not new for me. I've been having it for a while now and it's pissing me off, to be quite honest.

I tried with mods, without mods and the bug it's still there. I don't get a notification when the yoga class starts anymore like I used to months ago, the yoga instructor will just suddenly and quietly start the yoga class and no other Sim on the lot, from my household or otherwise, will join the class...because we simply can't. There is no option anymore to try to.

I've tried resetting the instructor, I've tried all 3 spa lots in different towns, I've tried with different households, I've tried asking the instructor to start the class myself (they will take my money but nothing happens). I don't know what else to do!!

My Sim can do yoga, that's not the issue, the issue is the yoga instructor.