Hi, I'm having the same issue.
I can add a guest to a private channel without any problem, but I can't add them to a shared channel.
Error: We can't add the selected users to the team right now. Try again later.
I have been trying to add the guest many times since the day before yesterday, but always the same error.
I reviewed all the policies and settings with the administrator account and everything looks fine.
Can anyone give me some tips on how to solve this?
Do I absolutely have to set up a "B2B direct connect" in addition to just adding it as a guest?
Thanks