If you do not enter a sensor code, you will be prompted to calibrate your Dexcom G6 CGM. You must enter your first two sensor calibrations on the same device, either the pump or the phone. After that, calibrations can be performed from either device for the remaining life of that sensor.
NOTE: It may take up to 15 minutes for the secondary device to register that a calibration was entered but it is not necessary to enter it on both devices.
Important note about Dexcom support:
For "no restarts" alert or physical problems with your sensor or transmitter, such as bleeding, bruising, skin reaction, adhesive issues, applicator issues, or broken wires, you should contact Dexcom using one of the options at dexcom.com/contact.
If you have paired a Dexcom CGM with your Tandem insulin pump, and your question isn't answered in this help section, you should contact Tandem customer technical support for all other issues by calling (877) 801-6901.