Why can't I add fund to Japan Suica in iPhone Wallet?

You must use a supported credit card; yours may not be.

Use Suica or PASMO cards on iPhone or Apple Watch in Japan - Apple Support

Various groups online have indicated that Suica has problems recharging from foreign-issued Visa and AMEX cards, and the JR East staff know it sometimes goes wrong but they don't know why.

Response to stephenwwu ; Apple Wallet ~ iPhone

Helpful in this link :

iCloud signed in / out & Devices

Requirements Needed

Suica Card : add , transfer , move to new iPhone

Add a Suica or PASMO card to Apple Wallet - Apple Support

having the same issue with the Apple Card. It used to work for adding funds to my suica but now it doesn’t work.

Same here. It happened all of sudden. However, my sister was able to add money to her Suica, and we are sharing the Apple credit card.

I think I figured it out. You can only add funds to the suica during Japan rail business hours so it will reject adding funds between 1Am-4Am Japan time.

I just tried during JR hour in Japan time and it’s still not allowing me to add money. 😞