It wasn't showing up for me initially. Had to de-link and re-link the fastag in the HP pay app, after which it started showing up. If it doesn't, you can use their paytm machine which has option of selecting fastag as payment option.
From within HP Pay app. Can use Amazon Pay balance to pay for the voucher. The voucher can then be added to HP Pay wallet and be used for fuel payment.
I was able to upgrade from Diners Black to Infinia last month. Had 8.4L limit, and spent >7.5L in the last 6 months. Had to go via an RM who helped send the form to Chennai head office and get it approved. If anyone in Bangalore meets the above criteria and wants to apply, feel free to DM me and...