If you see Connection Error while trying to scan your CGM, it is likely due to a proximity issue between the sensor and your phone. This error is not affected by Data or WiFi and must have something to do with NFC connection between the phone and CGM sensor.
Try scanning the sensor again by touching the top of your phone (the front camera/speaker) to the CGM sensor if you are using an iPhone. If you are using an android, you may need to research where your NFC is located as it varies between phone models.
Screenshot of the error: