EVA has blocked some award tickets to *A partners, including ANA. For North America specifically on LAX-TPE and YYZ-TPE route during the peak, and I can hardly find availability on JFK-TPE in Dec. From my experience ANA award ticket engine is the most reliable in *A, that is, generally you can book the award ticket from ANA only if you can actually see it on the website unless there's some YQ calculation problems.