I'm having trouble connecting the Tone app to my Mustang GT amp over Bluetooth – Zendesk

Make sure the amp is turned on, and you've enabled Bluetooth® broadcasting under Menu > Bluetooth on the amp
Make sure location permissions are enabled if you are using an Android device. Android devices running 6.0 and higher require location permissions to be enabled when using Bluetooth. On most Android devices, this can be done here: Settings > Apps > Permissions
On iOS 11, select 'Allow New Connections' or toggle Bluetooth off/on from the Settings screen
Be sure you are not paired to any other devices from your phone or from the amp. The app and amp should only be connected via the app, not Bluetooth settings
Do a Force Update on your amp:

1. Turn the amplifier off.

2. Press and hold the Encoder button and the left middle soft-key simultaneously and turn the amplifier on. Hold the buttons for at least 5 seconds and release.

Here are some options for resolving your issue:

On your phone/device, try turning Bluetooth® off, waiting a few seconds, and then back on again
On your amp, try turning Bluetooth® broadcasting off and back on in Menu > Bluetooth
If the amp is currently paired to a device that's still connected to it, have that device disconnect from it
If you are using your device's cellular data, make sure cellular data is enabled for the Tone app.

Here are some options for resolving your issue:

Try turning off your amp for several seconds, then rebooting it.
On the amp, go to Menu > Bluetooth to see if it's connected to your device.
In the app, go to Settings > Bluetooth to see if it's connected to your amp.
Connect your amp to WiFi so you can download any firmware updates.

If you're streaming audio over Bluetooth® to your amp, the app will have difficulty communicating with the amp while this is occurring. We recommend not audio streaming and using Tone for speediest results with Tone.