I didn't know there was a 3G sumup but my bluetooth sumup is similar - you don't know if it's gonna work or not. Resetting bluetooth on the gadget worked for awhile but nowadays

Now I have to try and process a fake payment & cancel it to make sure it's working before I get to the end of the journey and then process the real fare.
Problem is I'm not sure who's to blame. I've had the sumup gadget for 3 or 4 years now so maybe it's on it's last legs? But my phonemaker Xiaomi has a reputation for aggressively managing apps to increase battery life. And Google are getting it on the act now by removing app permissions if the app hasn't been used in awhile. So maybe it's Xiaomi or Google that's turning Sump off on my phone?