I'll be honest with you, there is no 'one size fits all' solution or guide to audio issues.
There are a bunch of operating systems, thousands of different devices, tens of thousands of audio different audio software and hardware elements, and an uncountable amount of permutations in how everything is set up.
This guide is going to be general information and troubleshooting.
General Information
Refresh Meetn
Any mysterious audio glitch on Meetn's side will almost always be resolved by refreshing the webpage and re-joining the Meetn. It works nearly every time!
Headphones
One of the most important hardware elements that contribute to good quality meetings is having headphones. If you're using open air speakers, like those built into laptops, monitors, or desktop speakers, you're likely to cause echoing. 99% of echo complaints are caused by this very scenario. Headphones fix that instantly.
Default Audio Devices
The most common cause of audio issues related to hearing no sound are misconfigured default audio devices, especially for Windows 10/11 users. While you're logging into Meetn or in a Meetn room, check your AV Settings (Audio Video Settings), and make sure Meetn is set to play and listen to the correct devices.
You can use the dropdown menus for microphone and speakers to text each of your connected devices. Try cycling through them to find the ones you want to use. If it's not the default setting, then that's likely the source of the issue.
Damaged Cables
For any AV device connected by a physical cable, make sure that the cables aren't damaged, crimped, cut, or over-bent. For example, you might notice your headphones make static-y or crunchy sounds when you move the cable around or rotate the jacks, this is evidence of cable damage.
Try Non-Meetn Applications
If a Meetn glitch is source of the issue, other websites and audio applications should work normally. Try playing a video on YouTube, turning on a song in iTunes/Spotify, or recording a voice sample in Audacity. If those programs work as expected with the same audio devices Meetn is using, then you can be sure the issue is not with your hardware.
Bluetooth Connections
If you're using a Bluetooth device, Meetn may not recognize it if you turn it on after you're already connected. It should, but may not always depending on system or browser settings. Give Meetn a quick refresh and you should see your Bluetooth device in the audio and mic dropdown menus.
Windows Update Disabled Your Device
An unfortunately common issue with Windows 10/11 operating systems, sometimes Windows Updates will reconfigure your audio inputs and outputs without your permission or notification. Luckily it's easy to fix!
Open the Start Menu and type "Control Panel". Open this application and will bring up the legacy Windows settings.
Then click the Hardware & Sound link, then click the main link for Sound or Manage Audio Devices. This will bring up a menu showing all of the speakers and microphones that your computer recognizes.
For both tabs Playback and Recording, scroll through the list and see if your preferred audio device has been disable or set to be not the default.
Find your desired default device, right click it, and set it as the default (if it's disabled, you can re-enable it here too).
⚠ Note: There is a difference between "Default Device" and "Default Communications Device". When Windows detects you're using a communication application or website like Meetn, Slack, etc, Windows will usually offer the Default Communications Device. Other sites and applications like YouTube or games will use the Default Device.