Several years late! but, I am trying something similar with CNA in an airline. So client does not have internet access until payment. Currently Apple Pay button is not visible, and trying to determine what needs whitelisting. We have whitelisted the domain as per https://developer.apple.com/documentation/apple_pay_on_the_web/setting_up_your_server, but this does not work.
Would be useful to understand how you managed to resolve it.
Thanks
Raj_Jayaraj23
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