My exported MP4 doesn't play the animation. It works in test mode. Can anyone help me?

When I export my animation, to video through Media Encoder, the resulting MP4 doesn't play the animation (using Quicktime for playback...the ultimate goal is to embed it in an email). In Animate, when I test it, the animation works perfectly. I am sure I must have some setting wrong here, but can't figure it out. Using current versions, of both (2022.) I have attached an image of my workspace below. I am brand new to this and would appreciate any advice you might have. What I am seeing when it is working properly are the color wheels spinning. Thank you! Alison