So even after hitting the reset pin it blocks the MAC?
I have seen this before on Videotron. Basically when I make up a MAC number (I don't use the real MAC since it's none of their business). Nor do I know if the MAC is reg this on their end someway/somehow (but likely is since IP is linked to MAC number of your device). So I always assumed the spoofed MAC already exists on the network, or maybe they compare this someway to like a master list and my made up MAC just doesn't pass the test (since the MAC does ID the company, make, and whatever else of the router). Or maybe someone is already spoofing the MAC number you are trying to use?
I don't really know in these cases. But I'd like to know if a Cogeco employee wants to take the time to explain this part.
So if it's a spoofed MAC, try a different MAC. If it's not a spoofed MAC, then Spoof it and that should fix the issue.