How to add my debit card to Apple Pay?

Uploading where?

If you want to add your card to Wallet and use it with Apple Pay, please note that not all card types, regions and banks support this. You can add credit, debit, or prepaid cards.

You can see how to set up your card for Apple Pay here:

Set up Apple Pay - Apple Support

Countries and Regions that support Apple Pay:

Countries and regions that support Apple Pay - Apple Support

You need to start by adding a new card to your Apple ID.

To add/delete a payment method, go to:

Settings → Apple ID → Media & Purchases → View Account → Manage Payment

Select Add Payment Method. Once your new payment method has been added, you can delete the old one. Remember, as long as you have ongoing subscriptions, you must add a new card before the old one can be removed. Once you have set up your new card for your Apple ID, you can try to set up Apple Pay, as described in my answer earlier.

You can find more useful information here:

Add a payment method to your Apple ID - Apple Support

If you continue to experience problems adding your card, contact Apple Support:

Contact Apple for support and service - Apple Support

I thought you should follow the instructions on that picture and contact Apple Support. I don't see any other solutions.

Contact Apple Support here:

Contact Apple for support and service - Apple Support

Hmm..

Instead of adding a new card, try if you can update your old card from https://appleid.apple.com

Sign in with your Apple ID, tap Payment Methods and then Manage payment method. Make sure your address is the same as that associated with your credit card.

Have you activated your new credit card through the card issuer?

If your new Credit Card is activated and you are sure that you have entered the information correctly in all fields, then I cannot see what is wrong. Are you a member of a Family Sharing?