You may try contacting Amex helpdesk
Contacted Amex. Their CS team'e superior professionalism standard has deteriorated over last few years and now they are only good at asking naive questions to waste time and misguide horribly. Once they told me to block my card and ask for a replacement so that reissued card will have a different number. My two Amex cards are having same last 4 numbers and it is confusing with tokenized cards with var websites/apps.
Anyways to get back with the issue:
1) Amex confirmed they are a partner with HDFC payment gateway
2) Told me "it look like HDFC has not updated their software to accept 4 digit CVV. Gave me contact no. of HDFC payment gateway and asked me to request HDFC to update the same. I told them to do that themselves as it is not my problem alone but of all Amex cardholders but they informed "merchant link is down
https://iforms.americanexpress.com/...pid_en_IN&evttype=0&evtsrc=link&loc_str=en_IN" else they could have done that (wtf is that🤔). Anyways I contacted HDFC on that given number but HDFC gateway technical team asked me to contact the merchant (the School here) to lodge the issue and they are bound by protocol and not to take feedback from random end users.
3) Went back to Amex CS team, they gave me contact detail of Amex Merchant Relationship team (don't know what role they have in this 😒) and they will guide further. I called their no but refused to discuss as their scopes are related to Amex merchant queries.
4)Went back to Amex agin and asked them to lodge complaint or escalate the issue. They only noted it as a feedback.
As for my initial mail to
pghelpdesk@hdfcbank.com' that their gateway is not accepting 4 digit Amex CVV, they haven't reaponded or acknowledged the mail yet. Still looking for workaround to make the payment using Amex to fulfill spend based criteria.