Can't add board passes or concert tickets to Wallet using "Add to Apple Wallet" button

I've tried adding Alaska Airlines and New York Philharmonic tickets to my Wallet using the "Add to Apple Wallet" button in the Alaska app and NYPhil email. In the Alaska app, I get the message "Unable to add boarding passes to Wallet. Please try using a different internet connection and try again." I switched from WiFi to data with the same result. On the NY Phil Safari webpage, I get "Error 503 Backend fetch failed. Guru Meditation: XID: 34912." I'm using an iPhone SE2 with iOS 17.4.1. I restarted my iPhone with the same results.

This is a recent problem. I successfully used Add to Apple Wallet to add tickets on 2/24/2024.

My partner did not have this problem with the Alaska app on his iPhone 14 Pro with iOS 17.4.1.