Microsoft 365 error 7q6ch , can't login to my microsoft account

I would not wipe Windows. This pattern points more toward the Windows Web Account Manager sign-in component than the personal Microsoft account used to set up Windows.

First, open Get Help, search for "sign in to Microsoft Office," and run the Microsoft 365 sign-in troubleshooter.

Then open PowerShell as administrator and run:

if (-not (Get-AppxPackage Microsoft.AAD.BrokerPlugin)) {
Add-AppxPackage -Register "$env:windir\SystemApps\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\AppxManifest.xml" -DisableDevelopmentMode -ForceApplicationShutdown
}

Get-AppxPackage Microsoft.AAD.BrokerPlugin

This checks and repairs the Microsoft Entra WAM package used by work accounts. Restart Windows afterward.

If the command returns an error or the issue remains, have your Microsoft 365 administrator review the failed sign-in in Microsoft Entra sign-in logs and confirm that the account has a license that includes the desktop Office apps.

I would not disable WAM or Modern Authentication as a workaround, since Microsoft does not recommend that configuration.