Some helpful troubleshooting blog posts.
Troubleshooting Apple Pay Suica #1 Suica registration problems
Troubleshooting Apple Pay Suica #2 Suica C102 Errors
Lost iPhone and Recovering Apple Pay Suica Recover Suica from a lost or stolen device
Migrate Suica to a new iPhone Move Suica to a new device
Renew Suica Commuter Plan How to renew Suica Commuter Plan after expiration
iPhone X Suica Problem iOS 11 bug causes occasional read errors with iPhone X
Fixing the Suica Lockout JR East locks Suica after 6 months of inactivity but is easy to fix