Solved. The solution: apparently I had accidentally disabled the "allow desktop apps to use microphone" setting. I re-enabled it. Turns out that it doesn't trigger any kind of error when windows doesn't allow bandicam to access the microphone, and your mic will still work when using apps downloaded through the windows store. But apps like bandicam won't work. If you're having this issue:

1. Press windows key or click search bar in bottom-left corner of screen

2. Type "microphone privacy settings"

3. Click that result that says "microphone privacy settings"

4. Find the button labeled "Allow apps to access your microphone" and flip the buttom to "on" - it will turn blue and the white dot will move to the right.

5. Exit out of the window and try recording. Audio should work now.

The reason it didn't work on bandicam but did on the other apps is that there is a separate menu to disable microphone access for windows-store apps, so those apps can sometimes access you microphone even if you disable the option for apps to access your microphone via the aforementioned setting.
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Bandicam will not record audio from any of my microphones, and all of them work. I have no trouble recording with the "voice recorder" app on my computer, and I downloaded another app too which records audio fine. It's not an issue of recording video and audio together either, because bandicam will not record audio even in audio-only mode and the video recording app that comes with windows still grabs sound from my webcam's microphone. Bandicam detects my webcam and records video on it, it detects all of my microphones, and even seems to fully recognize my sound cards (even has the "what u hear" feature in the list of audio devices) but will not record audio from any source. All my microphones are USB microphones, I am using an Audigy RX sound card, my headphones are plugged into that but nothing changes when I use the motherboard's built-in audio. I can find out which motherboard I have if necessary, as well as any other info that could help.

I receive no error messages while using bandicam, and screen recording works fine. All video functionality is working as intended, but bandicam is not recording any audio, either internal or external. No sound in recordings whatsoever, despite messing around with *every single setting* regarding sound in both bandicam and in my system settings. I have reinstalled the driver for every single piece of hardware on my system twice, just to make *absolutely sure* they are all the most recent and applicable drivers. I'm running Windows 10 and I had the most current hardware when I built my computer 4 years ago - everything should still meet or exceed bandicam's hardware and software requirements/recommendations.

Does anyone know what the issue could be? The only thing I can think of is that maybe some of the custom modifications I made to my registry and system services are interfering with bandicam. But i'm not sure how that would be possible since all of those things were done in the interest of system hardening and should have no impact on things like local video/audio recording that takes place entirely on my own system and not over a network. And it's not like I followed someone else's list of security modifications. I have a degree in cybersecurity, I did everything myself and was very careful to only disable services that I'll never want or need to use. The registry modifications I made just severed microsoft's telemetry services and ensures that the only way they can interact with my computer is to install updates with my permission.

It's possible that another program using the microphone exclusively is causing conflicts, even when other recording apps function properly. Before using Bandicam for recording, try turning off any background programs, such as chat apps, audio editors, or overlays.