Why is my Apple Pay restricted

What is the exact message you are seeing?

If Screen Time is restricting your Access to Apple Pay, then it can be shut off at Settings > Screen Time, and scroll to the bottom to Turn Off Screen Time.

If you see a message that your Apple Cash account is restricted or locked:

If Apple Cash is restricted or locked - Apple Support

If you see a message that you Apple Pay Later account is restricted or locked:

If your Apple Pay Later account is restricted or locked - Apple Support

If there is an issue with your Account, contacting Apple directly will be your best option:

Contact Apple for support and service - Apple Support