bluetooh 507 error

I'm trying to make an app for an android.
I will be using the app on the $20 phone I've bought from walmart 'alcatel' android version 6.0.1, model 4060w. And connect it to the RaspberryPi3.
The app I created on MIT app inventor should be correct, but I keep getting 507 error message when I try to connect the bluetooth.
I just want a simple app that can 
1)connect to the raspberrypi via bluetooth.
2)receive message from raspberypi.
3)alert the user when message arrives on a pop-up box.
4)and then, have yes or no button to return.

First uploaded file is what I have so far.
Second uploaded file is what I want in the end.

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See the Arduino and Bluetooth section of this FAQ

https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/mitappinventortest/2cd6Uz__xA0/cPQSiZpcDAAJ

Also, the sequence in Clock1.Timer should be

 if Connected then

    if bytes available > 0 then

       global = BTClient.GetBytes(bytes available)

        process global      (better for debugging via Do It)

The 507 error has many threads, use the search box in this forum.

ABG

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In the afterPicking you try to send a BT message before you actually connect. That cannot work.
Cheers, Ghica.

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