Fido says the calls won't connect because the conference hosting service needs to "add" the Rogers network.
No Cost Conference's support says they accept all calls, but that Fido is blocking.
Since the call just dies right after being dialed, I think Fido is blocking it.
What would it take to be able to complete this call, from my Fido, for which I am paying for "unlimited" North-America wide service?
Welcome to the community!
Unfortunately, I cannot speak as to whether that particular issue has been resolved or not. However, I just wanted to clarify that the No Cost doesn't necessarily mean free. The 712 area code is from Iowa in the United States. While the conference service might be free, depending on your cellular plan, long-distance charges would likely apply (see here and here). This thread is from a couple of years ago and I don't think Fido offers unlimited North American calling anymore (I'm not sure if any plans ever did include it). That said, Fido does offer Add-ons for US calling (see here, under long-distance).
After doing some research, calls to that area code and prefix might be more costly than for calls to other destinations the US. I'm not sure of any particular reason, but another provider listed some US area codes which they do not support with their Talk packages (see here). It is possible that Fido also blocks those area code and prefixes for similar reasons.
Hope this helps 😀