Shopware 6 Apple Pay just "Domain verification failed."

Hello,

we're using Shopware 6.5.7.3 and would like to offer our customers Apple Pay. The Domain verification has succeeded once already. Because of our Payment Provider the Identfifiers and certificates have to be grenerated a certain way, which we did not know at the time. Alas the domain has to be verified again. The problem is that the verification will not succeed anymore.

A new Merchant ID, Merchant ID Certificate & Payment Processing Certificate have been generated. Previously there had been error messages (paraphrased) like "Domain verification failed. The file can't be reached", which have been fixed. This time the only error message is "Domain verification failed". No extra explanation, just these 3 words.

The file "apple-developer-merchantid-domain-association.txt" can be reached inside the dir public/.well-know directory and the nginx acces.log documents a foreign Apple device accessing the file when the verification process is started in the Apple Dev backend:

"172.20.0.2 - - [29/Jan/2024:14:35:08 +0000] "GET /.well-known/apple-developer-merchantid-domain-association.txt HTTP/1.1" 200 5744 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML%2C like Gecko) Version/9.1.2 Safari/601.7.7" "17.179.144.226" 0.000 - . -"

Does anyone know what the exact error message "Domain verification failed." means? Which files are neccessary to verify the domain? Do files like merchant_id.cer/.pem/.key in %root%/config/apple-pay-cert play a role in this specific process?

Thank you very much for any insight