Upgraded my computer from Windows 8 to Windows 8.1.

It's on a domain that uses Windows Server Essentials 2012 R2.

In doing so, Windows Server Essentials no longer detects the computer. Do I have to run that /connect tool again??

When you say "no longer detects" what do you mean? Not in AD users and computers? When trying to log on does it give you a "trust" error of sorts?

Maybe somehow the upgrade knocked the computer trust off the domain. Just add the computer back to the domain.

The Windows Essentials dashboard showed the computer as Offline and still showed the OS as being Windows 8.

Rerunning the /connect tool fixed it.