“Card in transit” error when trying to remove Suica card from wallet

The only safe suggestion is to sign out of your Apple ID, restart the device and sign into your Apple ID again.

This 'wipes' active cards from Wallet and puts them in the cloud. You can add them again from "Previous Cards". It's a pain, but it should get Suica out of your device Wallet and parked in the cloud.

It means you didn’t tap out correctly on your last transit and Suica is still in transit mode. The card can be easily reset by any Tokyo area station staff, but cannot be removed from Wallet until it is reset to prevent losing the Suica balance.