Tabby Payment Issue – Debit Card Keeps Failing (ADCB)

I've been trying to make a payment on Tabby for the past 4 -5 days. Since they charge 1% for credit card payments, I wanted to use my debit card to avoid the fee - but every attempt failed.

With my deadline approaching, I ended up paying via credit card just to get it done. When I contacted Tabby's customer service about waiving the 1% fee (since the debit card failure wasn't on my end), they blamed my bank.

Here's what doesn't add up: I'm using the same ADCB debit card for other transactions without any issues. Only the Tabby payment keeps failing - yet my ADCB credit card worked on Tabby without a problem.

Both cards are from the same bank (ADCB), so why would the debit card fail on Tabby specifically while the credit card goes through just fine? Has anyone experienced this or know what the actual issue might be?