I have a hackable switch, oled switch, animal crossing switch, and Mario red and blue switch. they're not all the same. I think I may know why it won't let me play on my secondary switches. I think it's because I'm mass downloading on the primary. I'm thinking you can't even play on a secondary switch if you're downloading on the primary switch, but what happens if it tries downloading an update from a game on the home menu like it would by default? are you kicked out of the game on the secondary switch?
the problem has been solved. I didn't reach a limit, just had to clear the cache on the primary/oled switch, turn off the system, turn it back on. tested two of the three others and they work without issue.
I think I was wrong about there not being a limit or at least having not reached a limit. by the looks of things, I think only 3 units can be tied together with the same account. if you add a fourth unit, it's musical chairs behind which one will be deactivated. I need to call Nintendo tomorrow to be sure of this. if this is the case, I'm going to sell my hackable unit on here, possibly with a 1TB micro sd card included (and screen protector applied as well as dock, no cables).
alright, I think the problem has been solved. I called Nintendo again, and the guy told me to deregister my primary. the first system that signs in afterwards will become the new primary, so I immediately resigned in with the oled again. now, all four consoles are able to play games as I tested all of them. I may not have to sell my hackable system after all.