I’ve spent 15 years deploying on-premises versions of Microsoft Unified Communications, namely OCS, Lync & Skype for Business. During that period I did a lot of installations, but never had I done a full removal of the product. I guess that speaks to the usability of Microsoft Voice solutions. Once your in, the years just roll by like a good marriage. All good things must come to an end, now with Teams being purely cloud based no schema objects need to remain in Active Directory.

When attempting to do the final cleanup steps of the environment I was getting the following output when attempting Disable-CSAdDomain:

Disable-CsAdDomain : DomainUnprepareTask execution failed on an unrecoverable error.
At line:1 char:1
+ Disable-CsAdDomain
+ ~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:SourceCollection) [Disable-CsAdDomain], DeploymentException
    + FullyQualifiedErrorId : TaskFailed,Microsoft.Rtc.Management.Deployment.UnprepareDomainCmdlet
WARNING: Disable-CsAdDomain encountered errors. Consult the log file for a detailed analysis, and ensure all errors (2)
 and warnings (0) are addressed before continuing.

The HTML report presented me with some red:

Error: Cannot remove the Active Directory settings for the domain due to “FE” still being activated.

I had a few hours of scratching my head. I’d fully un-installed the Skype for Business Server software (minus the administrative tools) from the last Front End in the environment. Even the CMS had been deleted, so why did it think it was still active?! No CMS, means no jersey for a Front End server. I waited for domain replication but still no change.

Solution

The secret is to remove the last Front End server computer object from the domain. Install the tools on something else and re-run the cmdlet. Simple, but not obvious.

Thanks to Michael for the bright idea on this one.