Hello, Stan Laguerre
Welcome to the Microsoft community.
Hello, I'm sorry to hear about your issue with your wireless Corsair SE RGB headset where the volume control suddenly stopped working and got stuck at 100%.
I have done some research for you and this appears to be a known issue with the headset firmware, there are many users on the Corsair forums who have experienced the same issue as you, you can refer to the Corsair forums below it appears that there are also members who have resolved the issue by upgrading and replacing the firmware: Volume stuck at 100 - Gaming Peripherals & Audio Troubleshooting - Corsair Community
Disclaimer: This is a non-Microsoft website. The page appears to be providing accurate and safe information. Watch out for ads on the site that may advertise products frequently classified as PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
In addition, you seem to have already carried out many of the steps to fix it, my next suggestion is that you try contacting Corsair's official after-sales service, and after consulting with them, provide you with a firmware version adapted to your current system to give it to you.
Thank you for your time and effort to work on this topic.
Best wishes
Bobhe | Microsoft Community Support Specialist