Here's a simple checklist to try
- Have the measurements downloaded from the sensor completely? (Please note, if there are a lot of measurements to collect, this can take a little while)
- Does your phone have a mobile data or WiFi connection?
- Is the app open and in the foreground?
Check that you're connected to the sensor by opening the bottom panel in the app. It will tell you if there is a problem with taking the measurements from that sensor.