I think that page you’re seeing is from the “Page Addon”, which is an addon in the latest versions of Download Monitor ( https://www.download-monitor.com/extensions/ ).
Several years ago, I think that functionality was included in the Download Monitor plugin by default, rather than being a separate addon.
I have never actually used it, so I don’t know much about it. It looks to me like it would get in the way of how Email Before Download wants to work .. and, I guess that’s kind of what you’re seeing really. I certainly don’t see any way to make Email Before Download make its form appear on that page (which would then really just link back to that same page in a continuous loop probably, even if you could do it .. which you can’t I’m pretty sure .. that page is generated by the Download Monitor plugin .. of course, I could be wrong).
Anyway, I don’t think it’s made to work with that. Maybe you have that addon or some old version of Download Monitor. I think you need to turn that functionality off to make EBD work, but maybe there’s something I don’t know. You could pay $10 to M&S Consulting to get a definitive answer, but I suspect they’ll tell you you can’t do what you’re trying to do.