Hi @Laugh Larva ,
The error message "UserHasNoMailboxAndNoLicenseAssignedError" indicates that this is a license issue. It could be the admin has not assigned Exchange online license to your account yet, or in some cases it could be your admin has made a change lately in license settings. Since this is license a related issue, unfortunately, the only way to go about this issue is by reaching out to your admin.
Please refer to this article: https://answers.microsoft.com/en-us/msoffice/forum/all/something-went-wrong-we-couldnt-find-a-mailbox-for/6480660c-db0d-4c2f-b04d-9e01ab2a4f3d
Hope that can help you!