Hello! I understand your JBL Compact Connect app volume is stuck at zero on your Mac running OS X 10.15.7. Let's work together to get that sound back up.

First, can you tell me if the volume is stuck at zero only when using the JBL app or if your Mac's general system volume is affected as well?

Meanwhile, here are some simple steps we can try:

1. Check Mac's System Volume: Make sure your Mac's overall volume is not muted or set to zero. Click the volume icon on the menu bar and increase it a bit.

2. App Volume Settings: Open the JBL Compact Connect app and look for any volume settings inside the app itself. Sometimes the app has its own volume control separate from the system's.

3. Restart the App: Quit the JBL Compact Connect app entirely and reopen it. This can refresh the app and clear minor glitches.

4. Bluetooth Connection: Since the app controls your JBL device via Bluetooth, try toggling your Mac’s Bluetooth off and on again to refresh the connection.

5. Unpair and Re-pair: Go to System Preferences > Bluetooth, remove your JBL device by clicking the 'x' next to it, then pair it again.

6. Clear App Cache: While on macOS apps may not have a direct cache-clear button, uninstalling and reinstalling the JBL Compact Connect app can help clear cached data.

7. Reinstall the App: Uninstall the JBL Compact Connect app from your Mac, then download and install the latest version again.

If after trying these your volume control is still stuck at zero, the problem might be related to the speaker hardware or firmware. Resetting the speaker itself has helped many JBL users with volume issues.

For the JBL EON Compact, a reset usually involves powering it off, then holding down the volume up and power buttons simultaneously for about 5-10 seconds until it restarts. Could you please confirm your exact JBL model so I can give exact reset instructions?

Let me know what steps you've tried already or if you want to proceed with these. I’m here to guide you through!