The module typically activates as soon as the mirror or main fixture is connected to power. Some models require you to press and hold a touch sensor on the mirror for 3 seconds until a chime sounds.
Check that your source device volume is turned up. If it is paired to a smart accessory like a backlit bathroom mirror, double-check that the mirror's master control panel is active, and ensure the 12V power supply lines have not dropped voltage. If you need help setting up your device, tell me:
If you find a listing for the BL12-A3 on your favorite online marketplace, do not hesitate. Just ensure it mentions and USB-C . For under $30, it is the best insurance policy against boring silence you can buy.
The BL12-A3 module is designed for direct installation into products at the factory, and is often found in bathroom and home fixtures where you'd want a discreet audio source: