Boarding passes not showing in apple watch wallet

In my experience, that never happens. Your experience may be different, but I’ve never had an airline ticket/pass automatically added to my Watch Wallet.

Make sure both devices are updated to latest iOS versions and then unpair your devices and pair them again.

Please review the steps in the support articles I’ve linked to below to update your devices and then unpair and pair again both devices. Your Watch may show increased battery usage for the first 3 to 5 days after pairing your devices. This is normal. I hope this resolves the issue of adding tickets to your Watch.

Update iOS on iPhone - Apple Support

Update your Apple Watch - Apple Support

Unpair and erase your Apple Watch - Apple Support

Because of the security involved, tickets, passes etc. do not sync between devices. Some airlines do not support Apple Watch, some require you to add it separately and other want you to click the link you receive in the Watch, using the airline’s app, or link in email or text.

Yes, did you try adding it from your Watch? Did you try adding from the airlines app?

iPhone and Watch do not sync tickets, passes etc. They have to be added using methods I outlined above.