Try this in order on the Windows desktop:
- Make sure Bluetooth is turned on.
- Windows 11: Start > Settings > Bluetooth & devices and confirm Bluetooth is on.
- Windows 10: Start > Settings > Devices > Bluetooth & other devices and confirm Bluetooth is on.
- Check the JBL 720BT itself.
- Make sure the headphones are powered on.
- Charge them if needed.
- Keep them close to the PC.
- Turn the headphones off, wait a few seconds, then turn them back on.
- If the headphones are near USB devices plugged into a USB 3.0 port, move them away. Unshielded USB devices can interfere with Bluetooth.
- Make the PC easier to discover devices from.
- Windows 11: Start > Settings > Bluetooth & devices > Devices. Under Device settings > Bluetooth devices discovery, change it to Advanced.
- Windows 10: Start > Settings > Bluetooth & other devices > More Bluetooth options > Options tab, then check Allow Bluetooth devices to find this PC.
- Make sure Airplane mode is off.
- Windows 11: open the taskbar quick settings and confirm Airplane mode is off.
- Windows 10: Start > Settings > Network & Internet > Airplane mode and turn it off.
- Restart Bluetooth on the PC.
- Turn Bluetooth off, wait a few seconds, then turn it back on.
- Run the Bluetooth troubleshooter.
- Windows 11: run the Bluetooth troubleshooter in the Get Help app.
- Windows 10: Start > Settings > Update & Security > Troubleshoot > Bluetooth > Run the troubleshooter.
- If the headphones were previously paired and then removed, check whether they are still listed in Device Manager.
- Open Device Manager.
- Select View > Show hidden devices.
- Expand Bluetooth.
- If the JBL device still appears, remove it and try pairing again.
- Some Bluetooth devices can only be synced with one device at a time, so if the JBL headphones are connected to another phone or PC, remove them there first.
- If Bluetooth is missing or still not finding devices, update or reinstall the Bluetooth adapter driver.
- In Device Manager, expand Bluetooth.
- Right-click the Bluetooth adapter and select Update driver > Search automatically for updated driver software.
- If that does not help, uninstall the Bluetooth adapter, shut down the PC, then turn it back on so Windows reinstalls it automatically.
- If Windows does not reinstall it, open Device Manager and select Action > Scan for hardware changes.
- Driver changes can affect connectivity, so restart if prompted.