Not sure how to take a video with MacOS. I should add iOS works fine. The problem is on MacOS, I cannot add more than 1 photo to a diary entry. Once that photo is added, if I click on any others that are not yet added, the behavior is erractic. Sometime it will display the photo, but the plus symbol to add it isn't there. Rarely, I can add a second photo. But so far, I have yet to be able to add more than 2 photos to a diary entry despite many being available from Apple Photos and visible on the screen.
See the screen capture. I cannot add more photos to that entry.