So I’ve used the Reset App before (which looks like you can use it for the g5 transmitter). I had used this with one of the older g6 transmitters (80xx)(they recently released newer versions of g6 transmitters which have different SNs I believe 81xx (I could be wrong on these numbers)). Once I get my hands on a mac again, then I’ll try building the reset app again and will try to reset my new transmitter.
It is also possible to reset the g6 transmitters via Spike and xDrip I believe (I don’t have experience with either, but I plan to try out the iphone one this summer). Links to some posts on using spike/xdrip to reset the g6 transmitter:
Restarting G6 sensor failed? Help!
Tips on resetting transmittor on g6 via android phone