There are many possible reasons you might be experiencing issues. So let’s start with a few basic steps. I’ve added links to support articles that may offer solutions to many issues you might encounter.
Are you in a country or region that support Apple Pay?
Countries and regions that support Apple Pay - Apple Support
Does your financial institution support Apple Pay?
Apple Pay participating banks in Asia/Pacific, Africa, Europe Latin America, Middle East and United States - Apple Support
Confirm your region is set correctly.
Change the language and region on iPhone - Apple Support
Change your Apple ID country or region
If you’ve confirmed the above, please update your iPhone to the latest iOS, 16.5.1 or higher. Older iPhones may only support 15.7.5, but Apple Pay will function.
Update iOS on iPhone - Apple Support
Once updated, please do a forced restart of your iPhone.
Force restart iPhone - Apple Support
Make sure your are signed into your Apple ID/iCloud account on your iPhone.
Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support
Follow the steps in this support article for adding credit/debit cards to your Wallet.
Set up Apple Pay - Apple Support
If you experience any issues along the way, please note the error message and at what stage you experienced the error. Please reply anytime if something is confusing.