Under 9v power input BLE communication failed

Hello all,
I have a project using the Nano BLE allowing BT communication with an Mobile app.

When the arduino is powered with USB, everything is fine : arduino starting, visible from the mobile device and exchanging data with the mobile app.

Whe the arduino is powered with a 9v battery (I tested with different 9v batteries - the measured tension between Vin and GND is 7,9v-8,8v), the green led is on, but the BT is no more visible or reachable from the mobile application.

I am a bit confused about this issue. Does the BLE communication require more power? Is it correct to power to Vin & GND?

Thanks for your help.

The issue is likely you left the while(!Serial) statement in your code that many sketches use. This statement will make the Arduino wait for the Serial Monitor to connect.