I am seeing good availability for a flight I’m trying to book both via aircanada.com and via cowtool (SFO-YYZ-ADD-JRO) but when I try to book online I get the error:

“An error occurred and we were not able to complete the process. Please try again.(Error code: [40258])”

Is this something the call center could book for me, or phantom inventory? I am seeing the same flights available on UA in J for 250k miles (UA metal for SFO-YYZ in that case), but 115k miles on ac.com/Cowtool (with AC metal for first leg)