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Once you are in the "Connect to Microsoft 365" tab of the User profiles configuration page just follow the instructions on the page.
Because of security reasons it is currently only possible to connect the same Microsoft 365 tenant to one Jira Site or Sandbox.
If you want to connect the already configured tenant to another Jira site or sandbox, you must either configure another Microsoft 365 tenant for the original Jira site or unsubscribe and uninstall the app on the original site.
If you need this feature, you can vote for it on this page: Connect more as one Jira Site to the same Microsoft tenant.
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