I can't send data between Microbit and App Inventor via Bluetooth

The Bluetooth connection between the micro:bit and App Inventor was successful.

But there is no response when sending String Data.

I tested the data transfer between the serial Bluetooth terminal app and the microbit to see if it was a microbit problem, and it was successful.

App Inventor code is below.

Microbit code is below.

microbit-BLETest.hex (1.5 MB) BLETest_copy2.aia (289.5 KB)

Thanks in advance for your help.