It took our team several hours of frustration.

This list: https://developer.apple.com/documentation/apple_pay_on_the_web/setting_up_your_server#3179116

The verification expiry date is the same as the SSL certificate expiry date of the domain, so you can instead monitor your domain's SSL.

The verification expiry date is the same as your merchant domain's SSL expiry date, so the best way is to get a long expiry date. I don't find a way to automate this process too, so we have to manually download the verification file, upload to our domain, manually verify in develop console.

A registered domain’s verification expires when its SSL certificate expires. So if you don't update your SSL certificate with new one (i.e. new expiration date), then even if you verify again, nothing change.

Same here, we use Cloudflare to automatically renew the SSL certificate: Universal certificates issued by Let’s Encrypt or Google Trust Services have a 90 day validity period. Cloudflare tries to renew the certificate since 30 days before expiration. I also read the document and thought that after we updated the SSL certificate, "Apple detects the renewed certificate and the domain remains verified", and extend the expiration check according to the renewed certificate. But that did not happen, here is an example: SSL certificate expiration date: 5/15 4/17: Receive first warning email (i.e. 30 days before expiration) 4/17: Cloudflare renews the certificate, not sure before or after Apple's check 5/2: Receive second warning email (i.e. 15 days before expiration) We have to manually update the apple-developer-merchantid-domain-association.txt and verify again.

Same here, Apple still hasn't fix their bug about auto renewal check. Very annoying, have to manually upload file and verify again. We're using Cloudflare to auto renew certificate (90 days validity period), and the certificate we are using is Google Trust Services.

There is another thread, should be a bug: https://developer.apple.com/forums/thread/663425?answerId=751888022#751888022

Having same issue.