Could Not Set Up Apple Pay - An error occurred while setting up Apple Pay and then Apple pay is gone

This happened recently. I have been using Apple pay for a long while and I was trying to add a new card today.

Then I was seeing:

"Could Not Set Up Apple Pay - An error occurred while setting up Apple Pay"

I searched for solutions and saw a few threads:

https://discussions.apple.com/thread/6613712

https://discussions.apple.com/thread/250375131?answerId=250714736022#250714736022

I have checked the support pages such as:

https://support.apple.com/en-us/HT205630

I checked and tried whatever I saw:

1. Language & region setting is US on both iCloud and my device. iOS version, card eligibility, etc. are all right.
2. I tried restarting the phone a couple of times.
3. I tried sign off /back in iCloud many times.
4. I tried turning on & off WiFi many times and tried to check the Wallet with or w/o WiFi.
5. I have given enough time for all syncing operations.

None of these worked and my old added cards are gone.

There is no plus sign on the Wallet app anymore and I cannot see apple pay anywhere.

I checked these threads too but nothing helpful in my case:

https://discussions.apple.com/thread/8235619

https://discussions.apple.com/thread/250074004

Anyway I can fix this issue? Or the only option I'm left with is to reset the phone as new (I doubt whether that is gonna work for me either).

Thanks!