Symptoms
When you try to convert an existing domain from standard authentication to federated authentication in Microsoft SharePoint Online by using the Convert-MSOLDomaintoFederated cmdlet, you receive the following error message:
PS C:\Windows\system32> Convert-MsolDomainToFederated -DomainName <domain.contoso.com>Convert-MsolDomainToFederated : Microsoft.Online.Administration.Automation.IdentityInternalServiceExceptionAt line:1 char:30+ Convert-MsolDomainToFederated <<<< -DomainName <domain.contoso.com>+ CategoryInfo : NotSpecified: (:) [Convert-MsolDomainToFederated], FederationException + FullyQualifiedErrorId : Microsoft.Online.Administration.Automation.IdentityInternalServiceException,Microsoft.Online.Identity.Federation.Powershell.ConvertDomainToFederated
Cause
This issue occurs because the "Password expiry duration" policy in SharePoint Online is not set to the default value of 90 days.
Resolution
To resolve this issue, set the "Password expiry duration" policy to the default setting by using the following cmdlet:
Set-MsolPasswordPolicy -ValidityPeriod 90 -NotificationDays 14 -DomainName domain.com
