Press and hold the noise control button and the Digital Crown for 15 seconds, until the LED flashes amber, then white. After you reset your AirPods Max, you can connect them to your iOS or iPadOS device, or connect them to your Mac or other device.
How to reset your AirPods Max - Apple Support

Remove your AirPods Max from the Bluetooth settings on your connected device and then re-pair them. This can help establish a fresh connection and potentially resolve any connectivity issues.

Go to Settings > Bluetooth, then tap the Info button next to the name of your AirPods. Scroll down to the About section to find the firmware version. To use your Mac to check that your AirPods are up to date, make sure that you have the latest version of macOS.
About firmware updates for AirPods - Apple Support (IN)