when you do apple pay on web, if you are facing this issue:
Must create a new ApplePaySession from a user gesture handler
Which means you are trying to call apple pay without user's call(button click).
You should make sure you start the payment in a button click handler.\\
but if you are doing this but you still facing this issue, then you need to make sure you are not calling any backend or asychornize call and do payment in the callback. because apple doesn't like it.