Hello there! I'm glad to help you today!
May I ask what is the make and model of your computer? If you don't know the make and model or it's a custom, may I ask if you know the make and model of the motherboard?
Press Windows + R, type msinfo32, and hit Enter.
In the System Summary section, please provide me the three things below.
BaseBoard Manufacturer
BaseBoard Product
BaseBoard Version
Also, since you have done the MS diagnosis, have you checked in default devices that your JBL is on Stereo, and not on Hands-free mode?
-Right-click the speaker icon in the system tray
-Click Sound settings
-Under Output, click Choose where to play sound
You will see two JBL devices:
-Select JBL Tune 510BT Stereo
Click Set as default