I need to activate my iPhone 13 pro max from my iPhone 12 Pro max

Read this guide published by Apple ➔ How to remove or switch your SIM card. That guide has the illustrations that you can follow to remove the SIM card from your old iPhone and install it in your new iPhone.

ONE CAUTION: If you are using an eSIM then there will not be a SIM card in your iPhone 12. If you are not sure then please do not hesitate to contact your carrier for help.

Axel F.

Your active SIM card is still in your iPhone 12 Pro Max. Remove the active SIM card from your iPhone 12 Pro Max and install it in your new iPhone 13 pro Max. That should resolve this issue.

Axel F.