IAATM

Update: AC agent at the gate said that the fundamental issue was that UA failed to offload me from the original UA flight ORD-YYZ, and as a result, AC's system said the coupon had already been pulled and so AC was unable to make it work. I really wanted to tell the agent on the phone, but I was on hold (listening to Gershwin) as the AC flight closed and pushed back off the gate. Eventually, the UA agent came back to check on me, and said the supervisor was "still working on it", so I said thanks, but the AC flight had departed and it didn't matter anymore.

I then suggested that UA put me back on my original YYZ-ORD flight and simply force an overnight at ORD and allow me to connect first thing in the morning........so then I was put back on hold for ~30 minutes, when the phone suddenly went dead.....so maybe the Rogers network here in the transborder area of YYZ (4 strong bars) dropped the call or maybe the UA agent simply hung up on me.

so all in all, >120 minutes on the phone, spoke to many agents, and just now trying to get checked in and a seat assignment for my original flight that's delayed by 3+ hrs.