I just fixed this issue on my JBL Exteme 2:
Issue: JBL shows connected to device but not playing audio. I tried factory reset but ended up putting speaker into weird stationary mode, which locks you out of basically all functions of the unit.
Device was connected but not playing audio. I attempted hard reset but held down the wrong keys. I held down (JBL Connect +) and the (Volume +) buttons, after 10 seconds the device powered off and I was unable to power back on by pressing the power button. While in this mode, I could only get the power light to turn on when plugging the speaker into the power outlet, then the power light illuminates the color white instead of the Blue I am used to seeing. In addition to powering on only when plugged in, I can only get audio to play via 3.5mm in this mode as well.
To get out of this mode, you must plug the unit into power. Once the unit powers on and you see the power button lit up White, then hold the (JBL Connect +) and (Volume +) buttons until the unit powers off. Then unplug, press power button (do not hold, just press), and the unit will power on with the power button illuminated Blue. Now, reconnect your device to bluetooth and whallah!
In my situation, after connecting my device to the speaker via bluetooth I still had no audio coming from speaker although the phone said I was connected bluetooth. I hooked up my windows laptop to the speaker via BT, played a youtube video for a few seconds and the speaker worked perfectly. Reconnected my phone and now it’s working perfectly. I think a recent Apple update caused something weird to happen when connecting to bluetooth.
If you run into the issue of establishing connection via BT but no sounds, try connecting a totally different brand device to the speaker to trigger a type of internal reset.
If you attempt to factory reset, and end up hitting the wrong buttons and put your speaker into this weird mode that is not mentioned in any catalogs or anywhere online, just make sure to hold down whatever buttons got you into that mode everything should go back to normal. For me, I messed up by holding the JBL Connect + button and Volume up buttons, I got myself out of the issue by holding the same buttons. Took me a few hours to figure this out.. Hope this helps.