I tried to open it and clearly that’s a bug. I didn’t see any others with that same issue, but I didn’t try to open everything. I did open more than a dozen others with no problems. How many others did you find? If you could list the names of the videos that have with this problem DXO can address it.
Edit: There appears to be two items in the playlist that are marked private, Probably both bugs. Rather than using the playlist, tab use the videos tab. I believe all the videos that are available are in that tab, including the ones listed in the playlist tab.
In addition, here is a link to all the DXO Nik Collection Webinars with the ability to register for the upcoming ones. https://nikcollection.dxo.com/webinars/