I had the same problem with VideoDownloadHelper, and what did the trick for me was connecting to VPN and choosing a "NoSpy" server. Using CyberGhostVPN, btw, but I suppose other VPNs have that option as well.
The vids I'm talking about clearly show up on the models' pages... not sure what vids you're talking about. But the other guy mentioned specifically the "unavailable" videos, which is what i too was referencing.