Apple Watch can’t unlock the iPhone 13

I had this issue as well - also 13 pro max. i finally solved the problem by backing up my phone and then doing a full reset/reinstall.

Hello and welcome to Apple Support Communities tugba64,

Thank you for contacting us. You have come to the right place and we are happy to assist you. We’re glad you reached out. It’s important to us that your concerns are addressed. You have updated to iOS 15.0.1 per the article you are using, so our next recommendation is to contact Apple Support. You can contact them from the link below.

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Best regards.