This sounds super weird. It has to be your cardo since you've tried to pair it with a number of different devices. If factory resetting the device didn't fix it then I would suggest that you are down a cardo unit.
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I really hope not. They didn’t make it idiot proof :( Guess I’ll engage with support… hopefully
Do you have a separate volume control for music and other audio while paired to Bluetooth? I had that happen to me with my Sena a while ago
Ah yeah meant to say I tried that too. The Cardo app allows you to adjust individual volume levels, but playing with those doesn’t have the desired effect.
Sounds like you're already going down another path, but Fwiw the individual audio levels in the cardo app do not do exactly what their names imply imo.
Background music is effectively just music level, for instance. I assumed it was the level music dropped to when someone talks or a phone notification plays, but no. It affects the normal music volume. The app explicitly says it's for during an active call, but it is wrong. You want it at 100% always afaik.
Your phone audio settings may also be separate for different types of audio, as another comment pointed out, and these settings are NOT the same as the ones in the cardo app. You need to turn them both up.