Hello, Holly B-0602
Welcome to the Microsoft Community.
Thank you for your feedback on your issue here, based on what you've described, it seems that your Realtek audio driver is missing or not installed correctly, which could be the reason why the microphone is not working properly.
First of all, thank you for sharing the information, you seem to have already performed some troubleshooting steps, which is a great sign that you are a researcher and scholar. Your issue should still be driver related and I will further advise you on fixing it.
First of all, since your Realtek driver seems to be missing, you need to reinstall it. You can follow the below methods to do so:
Method 1: Automatic update via Device Manager
Press Win + X and select Device Manager.
Expand the “Sound, Video, and Game Controllers” section.
Right-click on any audio-related device and select Update Driver.
Select Automatically search for updated driver software.
If Windows finds an update, install it and restart your computer.
Method 2: Download Realtek Drivers Manually
Visit the official Realtek website to download the latest Realtek HD audio drivers for Windows 11.
www.realtek.com
Once downloaded, run the installer and follow the on-screen instructions to complete the installation.
Restart your computer after the installation is complete.
Disclaimer: Microsoft provides no assurances and/or warranties, implied or otherwise, and is not responsible for the information you receive from the third-party linked sites or any support related to technology.
Sometimes Windows may prevent applications from accessing the microphone.
Go to Settings > Privacy & Security > Microphone.
Make sure Allow applications to access the microphone is turned on.
Scroll down and make sure that the application you want to use (such as a game or communication software) has permission to use the microphone, plus make sure that your headset is plugged into the correct jack. Most headphones have two plugs, one for audio (green) and one for microphone (pink). Make sure they are plugged into the correct port.
Also if it's easier for you it's recommended that you take a screenshot of the Device Manager screen for sound cards etc. Here I'll check if some drivers are missing for you.
Best regards
Bobhe | Microsoft Community Support Specialist