Previews & snapshots not working on some of my cameras for 9 days...

Great call on power cycling the system! Glad to hear this worked. As for downloading a snapshot, this works best when visiting the snapshot in the timeline view with the timeline paused. Once the timeline is positioned over the snapshot, tapping the more actions (circle with 3 dots) option at the bottom right, should display a “snapshot” option. This operation will need photos permission, if not already accepted.