One possible cause for this problem could be that your iPhone/iPad was connected to an external audio device, such as AirPods, headphones, speakers, smart TV, CarPlay, or any other device during the recording.
To troubleshoot this, please try disconnecting any external devices and attempt to record a video again.
If the issue persists, I recommend restarting the Zoog app and try to record again. Here's a guide if you're not sure how.
Please give these steps a try, and if the problem continues, feel free to contact us for further assistance.