Hi Patrick,
I understand you encountered the issue with Set-MsolDomainAuthentication cmdlet.
The Set-MsolDomainAuthentication cmdlet is used to change the domain authentication between standard identity and single sign-on. Actually this cmdlet will only update the settings in Office 365.
Currently, please use the following cmdlets instead.
Convert-MsolDomainToStandard
Or:
Convert-MsolDomainToFederated
After that, please check whether the issue still persists.
Thanks,
Kevin Cui