White square with blue dotted line

[Coachwalker]

Any idea what this is? It keeps interrupting my progress and doesn't seem to do anything

Thank you in advance

[#2 · Accepted solution]

That's the login dialog. Make sure you install the latest updates for both Office and Windows, as many such issues have been already patched. There is additional troubleshooting information here: https://docs.microsoft.com/en-us/office365/troubleshoot/administration/connection-issue-when-sign-in...