Some iPhone users after upgrading their iPhones to latest iOS released from Apple are facing issue with video shot from their iPhones, Some videos from a few months ago those were saved to my camera roll won't play. Users only see little loading circle like it is trying to load the video but it never plays the video. All videos were playing before the upgrade and saved successfully. Since after the latest update some of my videos plays fine and the others just have the loading circle. The issue is reported across almost all iPhone models including iPhone 5, iPhone 6 and iPhone 7 as well.
Fix for the issue when iPhone won’t play saved video
Fix 1: iCloud sharing
For many user this fix worked successfully and the solution is to select the videos (All of them or one by one, makes no difference) and press the upload button.
The press iCloud Photo Sharing. It will show a timer saying "preparing". Once this is done, the video should now play.
Fix 2: Load the video first
Select the video, but instead of playing it, there is a tab at the bottom of the screen, chose the icon 2nd from right (looks like music sheet) 3 horizontal lines. It should now show circle slowly filling up and saying downloading video. Depending on the size of the video shouldn't take more then a few minutes.
Fix 2: Manage storage
Make sure your iPhone storage is not full, in case it is please make sure to delete some unimportant data from it. Hopefully your videos will play again.
Go to: Settings>General> Storage> Manage Storage