Thumbnails are not available for locally stored content. If you eject the storage device and view from a computer, are you able to view the clips?
Same issue here. It worked fine until a few days ago. Now I can see some recordings in my IOS app, but most of them appear blank. Recordings are on the USB as I can view them on my home computer. Issue for both of my cameras. Please fix.
I fixed this problem by using the option in the Arlo app "Delete downloaded video's" This does not delete them from the cloud or base station, but only in the app. Afterwards my video's were available again and I could download them.