Red bars on the CGM graph in Control-IQ represent periods where basal delivery was stopped. Periods where basal delivery was decreased do not appear with red bars. It is possible to program a manual bolus while basal is suspended in Control-IQ, unlike in Basal-IQ.
Tandem handles issues with the connection between your Dexcom transmitter and t:slim X2 pump, questions about calibration, the “---” display, and sensor failures after the 2-hour warmup period. To report a sensor failure after the 2-hour warmup period, visit tandemdiabetes.com/G6Form
For all other CGM issues, including sensor failures during the 2-hour warmup, “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.