Are you unable to invite users or users unable to join meetings? Are there any screenshots of the error? (Note: Please pay attention to hiding personal information)
To invite external users to a meeting in Microsoft Teams, click New Meeting, enter the full email address of external user in the “Add required attendees” field, and you will see a pop up window says "**Invite **@domain.com", click on the pop up window to add the user to this invitation email. For your reference:
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