How can I get a ticket issued from a flight pass, where availability in the required booking class is given, but the travel time seems to exceed flight pass algorithm rules? The travel time is so long because few flights are going.

The situation:
Back in February, I bought a Flight Pass for flights between Western Canada and Europe in Economy Class. Requirement: Availability in booking class V, operated by AC/ACx/ACr. But now the Air Canada agent tells me that "not all flights" are eligible for Flight Pass bookings, even if booking class V is available. They never said that when they sold me the air pass.

I am trying to use a segment of my Flight Pass for departure Sept 26 from YXY to BRU - one of the few European destinations Air Canada is still flying to. However, when I try to use the flight pass, the AC website throws an error: "RC=400 component=EIP” Whatever that means. On other days, that error does not appear, but it still doesn't work.

There is availability in booking class V in a single fare: "SHOULDER SEASON MIDWEEK ECONOMY OW V UNBUNDLED FARES APPLIES FOR ONE WAY FARES FOR ADULT".
Sept 26 AC 8890 YXY to YVR
Sept 27 AC 304 YVR to YUL
Sept 27 AC 832 YVR to BRU, arriving Sept 28

The problem, I presume, is the 23:15 layover in YVR, or the arrival 2 days after departure, one of which must throw the flight pass algorithms off. (There is another routing available in V with a simliarly long layover in YUL and identical total travel time - also a now-show on the flight pass interface.)

It is not that I'm trying to pick a weird routing. Actually, that is the most straightforward routing these days, as so few flights are going and Air Canada has, unusually, moved the YXY flight to the early morning.

I had one agent tell me that they'd be happy to book it for me, but I'd cost two credits, which is robbery. The same agent said to call again and talk to other agents, maybe one would do it for a single credit. So I called back later. That agent checked with the helpdesk and then told that there is nothing anybody can do because "that is how the system is built" and "not all flights" are available to flight pass holders. Even though there is availability in V in a single fare.

I offered to buy the ticket as a normal ticket, then exchange a flight pass credit for a refund. That was denied. I suggested that we first book YVR-YUL-BRU and then immediately add the YXY-YVR leg. Denied as well.

The agent suggested going through Customer Relations but added that it may take 40 days to get a response. Useless.

What to do?