Hi @Graham Mitchell
According to your error report, is your problem caused by being unable to log in to M365 on your personal computer?
Teams tag is mainly focused on the general issue of Microsoft Teams troubleshooting. According to your description, your question is related to Microsoft 365, which is not in our support scope.The following suggestion is just for your reference:
This error normally occur due to one the following reasons:
1.The user has already enrolled the maximum number of devices allowed for the account.
2.The device is blocked by the device type restrictions and manage by organization.
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