iPhone 12 Pro Max blocked due to forgotten passcode

Hello,

See this:

If you see an iPhone or iPad unavailable message or Security Lockout screen 

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled 

If you forgot your iPhone passcode, use your Mac or PC to reset it

Good luck.

Might be a good idea to suggest to mum that she write down the new passcode and keep it in a safe place......even if she is sure that she will never forget it.

If you know the new passcode, you could keep a copy as well. It will likely come in handy.....you just don't know when.