For the world "Thad Tiny Library" it is not possible for a pc user to join an instance that a quest or android user has created, but the other way around works just fine. PC users will get the error message:

"You can't join this instance because it is not compatible with the latest world version"

I tried reuploading the world for both windows and android to a seperate test world and the problem happened there as well. Clearing the cache, changing to the beta version on windows and quest, or updating the world sdk to version 3.10.3, all didn't help to resolve the problem.

A quest user in a pc instance can invite other pc users to it, though.

This is the world link: