why did the suggest on lock screen option for my boarding pass go away?

If you go to settings>Touch ID/Face ID & passcode>allow on lock screen- make sure wallet is turned on here. If it is turned on, try going to settings>general>reset>and reset all settings.

Use your passes

Some passes automatically appear at the right time or place because they include information based on time or location. For example, when you arrive at the airport, your boarding pass should appear. If your pass has a contactless symbol on it, you may be able to use it at card readers and point of sale terminals that display this symbol.

You may need to slide to unlock your device to display and scan your pass.

With iOS 9 and later and your iPhone 6 or later,1 there are two quick ways to use a pass:

• If you have a credit, debit, prepaid, or store card in Wallet, or a rewards card that works with Apple Pay, open Wallet from the Lock Screen by double-clicking the Home button or by double-clicking the Side button on iPhone X and later. 
• If you turned on Automatic Selection for a rewards card, store credit card, or ticket, use that pass by tapping a pass notification or tapping the pass in Wallet. Then hold your iPhone near the contactless reader. You may need to authenticate with Touch ID or Face ID.

If you want notifications for things like flight updates or coupons and sales for nearby stores, follow these steps:2

1. In Wallet, tap your pass.
2. Tap .
3. Tap the Notifications button to turn notifications on or off.

To turn on notifications for all your passes, go to Settings > Notifications > Wallet, turn on Allow Notifications, and turn on the alerts that you want.

Learn how to use your student ID card in Wallet.

Just found this. It’s an issue with Southwest app.

https://www.southwestaircommunity.com/t5/Check-In/Boarding-Pass-Notifications-on-IPhone/td-p/93874/page/2

I have exact the same problem with the same time frame. Coincidentally, I got an Apple Watch around middle of July. The boarding pass has not shown up on lock screen since. Not sure if it’s related to Apple Watch.

That is all the information that is available.