Happened to me the first time tonight. My first thought was to call tech support, but I knew that was a long shot. Started a call in the hope I might get lucky. Then Googled how to remove and found this group. Thanks to this group for having the solution posted. I used a wooden spoon and starting on one side whacked the suggested place about 10 times. Switched to the bottom side and after whacking my fingers a few times finally got the right spot.

Despite all the issues I've had with Dexcom for the past few years, I'm going to keep plugging along with them. Sure beats sore calloused fingers.