Error 503 not valid MAC address

I'm going to make an RC car with ESP32.
When I try to connect ESP32 with app inventor, the message "Error 503: The specified address is not a valid Bluetooth MAC address" appears and I cannot connect.
What's the solution?

That MESSAGE procedure is sending your app into a coma when it is called.

It does nothing but call itself ad infinitum, until it fill memory.