Hello, I have a couple of questions trying to figure out the scenario here.

- When you say "we have guest users" do you mean that they are already in your Azure AD with guest accounts?
- Are any federated? (trusted with no guest account in your tenant?) That is, have you set up external access in Teams? If so, are you using allow or block lists?
- Is this happening for only one user?
- Have that user signed out from all Teams sessions and tried joining again?
- Same behavior desktop and online?

For the record you can have anonymous access turned off as guest users are part of your org. with guest accounts and federated users are considered authenticated by the trust.
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