All Reolink NVRs
Please refer to the steps below to troubleshoot:
Step 1. Make sure the loudspeaker attached to the "audio out" jack of the NVR works fine. The USB cable of the loudspeaker also needs to be plugged into the USB port of the NVR to power it up.
Step 2. Go to the menu of the NVR. Make sure the audio output of the NVR is enabled like the picture below.