GroupMe is now up! Service expected to be remain stable.

"Merry Christmas! Oh, btw, we're down at the moment," was the first status message when things went awry a couple hours ago.  As of one hour ago, the service is still completely down.  The folks at GroupMe have apparently identified the issue as "service provider" related and they are feverishly working to get things restored.  What perfect timing right?  Christmas Eve, and things go dark.  There are no details about what actually happened and GroupMe has not offered any estimates as to when service will resume.  In the meantime, if you have been messing around with GroupMe and getting frustrated, it is not you.  We will check on the status from GroupMe and update you when we can.

UPDATE: Some configuration changes may be enabling you to use the app or SMS, but GroupMe is reporting impaired service still.  

UPDATE 2: Service has been partially restored, though some users may still encounter problems while GroupMe works on a final fix. 

UPDATE 3: GroupMe now reports that while their service provider may continue to have some issues, GroupMe messaging, App, SMS and web will remain stable. 

source: GroupMe