App store connect reject build because missing NSBluetoothAlwaysUsageDescription key

You'll need to add the purpose : Why your app requires Bluetooth to be enabled. Something like this :

<key>NSBluetoothAlwaysUsageDescription</key>
<string>App uses Bluetooth to find, connect and communicate with nearby devices. Please grant access.</string>

Just putting a purpose without knowing what is using it would not be the best way to handle this.

I had this exact same issue. When I did a grep search I found that there is some reference to CoreBluetooth.framework inside my project.pbxproj

I removed the reference and building the app went fine. Uploaded to Apple and it got through so this worked for me.

To search use the following command

grep -r -a CoreBluetooth.framework ProjectFolder

The accepted answer is right but not full. You really need to add this key into your .plist file. But NSBluetoothAlwaysUsageDescription added in iOS 13+. If you target iOS below 13, you also need to add NSBluetoothPeripheralUsageDescription in addition to first key.