[kirkf]

I had this same problem in Manitoba in September.
The registry agent simply couldn't wrap their head around the idea that the vehicle was last insured before computers existed.

After two weeks of this mess I gave up and went to a different agent and they did it in five minutes with a simple phone call.

So the first thing I would do is go to a different insurance / registry outlet and try again.

You could also look up your local vintage car club and give one of the members a call. I'm sure they have been through it as well.

Kirk