Thanks for the feedback. I got round the issue by changing the order of some flights. I reversed direction and started out with a YVR-DFW-EZE route. That saved me a segment, so I was able to tack on my final flight back home to SAN

I also discovered that it’s about $2K cheaper to start in Oslo, rather than in Vancouver (about $4K cheaper than ex-US). That said, a positioning flight to YVR costs around $150-$300, vs around $3K to position to OSL, so a bit of a false economy here.

I was also able to get round the “cannot price error” to on another sample itinerary. I was just trying to see what was possible and how timings worked out and as you stated, the tool picks the shortest duration. I decided to opt for a longer layover on my 4th, or 5th segment and suddenly the tool was able to fully price the RTW ticket.