Same Microsoft account, multiple devices, all in one world. (NS & iPad)

My kids are so young they use my Microsoft account to play games. I’m able to load up a world on my iPad and my son could join on the Xbox and vice versa. Just tried to join my daughter on her Nintendo switch and it shows that someone’s online but it will not show it as available to join. I also just bought a years worth of Nintendo switch online thinking that was the problem (it turns out it’s not) so please please please make it so that iPad and Nintendo Switch can join each others games with the same Microsoft account.