The second page of my Apple Wallet got deleted by error

You don’t add tickets yourself. Tickets, boarding passes, hotel room keys, etc. are all added from the ticket/passes issuer’s mobile app, secure website, email or text. You cannot add them directly yourself.

There is no second page. The current procedure is to use the secure methods the ticket issuers support. If you physical ticket has a barcode or QR code and you need to scan it, just use the Apple Camera app and if the codes support Apple Wallet it will be automatically added to the Wallet app.

Are you traveling or have you traveled recently? What region is your iPhone set for and what region is your Apple ID set for?

Confirm your regions are set correctly.

Change the language and region on iPhone - Apple Support

Change your Apple ID country or region

Contact the airline you’re flying with (British Airways?) and seek their guidance. I have status with American Airlines (a One World/BA partner) and even with my status I have never been able to add boarding passes until I check in a few days before scheduled departure.

You can try to add that card again to see if the issues persist

What does that mean? Boarding passes usually can’t be added until you check in for your flight.