If the battery on your t:slim X2 insulin pump falls below 20% and you are not actively using the t:connect mobile app, the mobile app will stop wirelessly uploading pump data and providing pump alerts/alarms. This Low Power Mode is a feature available in the t:connect mobile app (iOS smartphones) starting on software version 2.8.2 and later.
To restore the connection with your pump and resume normal use of the t:connect mobile app, charge the battery on your pump. After charging your pump battery to over 20%, there may be a brief delay in updating the main trend graph when you open the mobile app.