I've on day 4 of my first Gen 4 sensor. After the first day it's been very reliable. Yesterday I had an hour of the "Wait" hourglass followed by ???. After that the sensor kicked back in and seemed to work great. Mid-morning today I got a sensor failure alert.
Although I had some 7+ sensors replaced when they weren't working well, I think I only had 1 sensor failure in 1-1/2 years. So it's a bummer to start my Gen4 career this way. But I've got a new sensor inserted and will hope that the first one was a fluke.
I got my Dexcom on November 12th. Of the 7 sensors I have used so far, 2 have failed. One after 6 days with funky readings like 55 for a fingerstick and 110 for the Dexcom. They replaced that sensor and most recently I had a sensor which I put on my left thigh, after having fantastic results on my right thigh for better than 11 days. The left thigh, not so much, I almost immediately got the ??? then an hour glass, then 3 readings and back to the ??? so I called and since it was fairly late my time I decided not to use the call back feature and just stay on the phone and yes it did take close to 45 minutes of waiting before I actually talked to someone and they of course cheerfully replaced the sensor. But of the 5 that I have used successfully, most have lasted at least 10-12 days and 1 has lasted 14 days without issue, so I am very pleased with this product. I have been impressed with how accurate it is and I like their software as well, though I find it is very similar to many other programs in that it favors high blood sugars over low ones, but that is another discussion all together.