Well I figured it out - for anyone still encountering this issue: My company has one domain to service multiple locations/storefronts. Each location has it's own separate Payment Processing account, requiring a unique Apple Pay Payment Processing Certificate/MerchantID. The docs and responses here made me think subdomains would be required, which is a headache in itself - especially since the Apple Pay Session must be started from that subdomain (not the parent domain). SOLUTION: If you register multiple MerchantIds within a single Apple Developer Identifier - all Domain Association Files tied to a certain domain are the same. So if you verify for one MerchantID, then add that same domain to another - it will count it as already verified. No need for subdomains. No need for swapping out Domain Association files. Really wish that Apple had made that clear.
Topic:
App & System Services
SubTopic:
Apple Pay
Tags: