After replacing my right earbud the new one does not connect/pair .

Hi MCLS_Apple

welcome to the Apple (user-to-user) Community!

re: "After replacing my right earbud the new one does not connect/pair" .

Do you need to update your software to pair AirPods: About iOS 17 Updates - Apple Support : 17.1.1 is the latest.

To update your device: Go to Settings > General, then tap Software Update

or

Wondering if Apple support's online article (link below) may help:

How to: Set up your replacement AirPods or charging case - Apple Support

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re: "Everytime I receive a notification saying that My Airpod Pro mismatched and can not work together."

There's an article on mismatched AirPods: If you see an alert that says "AirPods Mismatch" - Apple Support

If needed:

AirPods Support Website:

Find all the topics, resources, and contact options you need for your AirPods....

AirPods Support - Official Apple Support

All the best :-)