Should have specifically asked for 10k retention offer : https://www.technofino.in/community/threads/axis-magnus-offering-retention-points.16346/post-329111
Not much info on exact MCC, @jack333 @VISHESH_BANSAL can help
Here's some limited info : https://www.technofino.in/community/threads/parkplus-changed-mcc.17886/
and https://www.technofino.in/community/threads/5-cashback-on-utility-bill-payment-from-hdfc-millenia-on-amazon.6715/post-352997
Check your emails and SMS from May, they must have sent notification regarding this offer (mostly related to Smartbuy platform)
remove spaces (before/after) or any invalid characters
Some more ways :-
1. https://www.technofino.in/community/threads/merchant-catagory-code.10012/post-162607
2. https://www.technofino.in/community/threads/free-amazon-gift-card-credit-card-to-bank-transfer.10564/post-193428
3...
If payment is failing after entering OTP, then something's wrong on your end. Check the common reasons in my reply and also the email for tnx failure
So what expiry month & year did you actually enter when making the payment?