The CM390 uses a hideable boot mode. Some apps (like Bluetooth tray apps) hide audio devices.
A: That is not a driver issue. That is Bluetooth codec negotiation. The CM390 supports SBC and aptX. Right-click your speaker in "Bluetooth & devices" > Properties > Disable "Handsfree Telephony" to force high-quality audio mode. ugreen bluetooth 50 usb adapter cm390 driver install