Help with system transfer?

So, here's the deal. I bought Mario Wonder on my original Switch, and then eventually got a Switch OLED when that Switch finally gave up the ghost. When I did, I got the Mario Wonder bundle because it was somehow cheaper than getting an OLED by itself. Because I already had Mario Wonder, I couldn't actually register the preinstalled software to my account, which wasn't really a problem... until now.

So, does anyone know what I can do to solve this? Been trying for the last hour with no luck.