why am i unable to update or restore my Iphone 11 pro max?

Try putting your phone into recovery mode.

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

Have you put your phone in recovery mode?

'Press and quickly release the Volume Down button. Press and hold the Side button until you see the recovery mode screen with the "Connect to iTunes" screen, then release it. Select your device in iTunes. You should see a message in iTunes saying that your ‌iPhone‌is in Recovery Mode.'

Are you still able to use the phone? Because if so, you can update from the phone itself. (Settings-General-software update.)