Yes, a QR code did pop up. The problem was that scanning it (multiple times, with iPhone camera, with two different QR readers) resulted in nothing, all that came up was some page on the Southwest Airlines site, which had absolutely nothing to do with what I was trying to accomplish.
I have given up on this specific misfire. I'll print the pass and carry it, like our cave-dwelling forbears of yore used to do. It's not the first time I've had trouble adding passes or ticket to Wallet, where it would be so convenient to have them. But consulting the Apple support pages and the community here has never resolved it.
I'll move on. Thanks for trying to help.