If there is no audio in live view on Reolink NVR, please kindly refer to the steps below to fix the issue.
Step 1. Attach the NVR to a monitor/TV (needs speaker on the hardware) via the HDMI port. The resolution of the monitor/TV should be 1920*1080 or 1080*720, or the NVR will not have a sound output with monitor via VGA.
Or if you don't have monitor, you should plug a loudspeaker box into the audio out jack at the back of the NVR to get the sound output for the cameras added to the NVR.
Step 2. Go to Menu->Display->Output, make sure that the audio output of the NVR is enabled like the picture below. Please check the Audio box in the picture.
On Reolink app:
Please kindly check whether you switch on the speaker like picture below.
And please kindly enable Record Audio option like picture below.
On Reolink Client:
Please kindly make sure the speaker like picture below is enabled.
And please check whether you have enabled Record Audio option.