I'm using photoshop v20.0.6. Recently I found out the animations I make on photoshop can't be played on save for web window. (when you hit the play button, it doesn't show the animation) but I still can save the GIF file without a problem. However, I tested the preview on the former version (v19.1.9) and it started to play the animation but with hiccups. I’m not sure if it’s the problem with the latest update or something else.