This has worked once for me on my iPhone 6, iPhone 7 and iPhone X. I don’t know what the problem is, but it worked on one trip a few months ago. Strangely, it stopped working on Alaska BPs as well about the same time it worked on my WN app.

Even stranger, if I fly AA, I am able to access the BP from the lock screen just fine, so it shouldn’t be an app setting since everything is configured the same. It works great on my wife’s phone, a fact that she constantly reminds me of.