AirPods Max randomly turns off noise cancellation and transparency mode

Hi CXLVII,

Thanks for contacting Apple Support Communities!

We understand that Active Noise Cancellation and Transparency mode are disabled for your AirPods unexpectedly.

You've done a great job troubleshooting so far! We appreciate you sharing those details.

We'd also suggest that you ensure your iOS is up to date so that your AirPods firmware is also up to date. If you need help to update your iOS, this article will guide you: Update your iPhone, iPad, or iPod touch - Apple Support

"Update your iPhone, iPad, or iPod touch wirelessly

1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see two software update options available, choose the one that you want to install.
5. 
6. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.

You might see that your device is up to date and that there's an upgrade available. For example, even if your device is up to date with the latest version of iOS 14, there might be an option to upgrade to iOS 15. You might want to upgrade iOS when you pair an accessory with iPhone."

Have you noticed if it's switch on your iPhone or via your AirPods? This article explains how this feature works: AirPods Pro and AirPods Max Active Noise Cancellation and Transparency mode - Apple Support

If you have any other questions or concerns, we'd suggest that you contact Apple directly to help you to determine your next steps, if needed. You can reach them here: Contact - Official Apple Support

Take care!