Animate CC export video quality too low for adobe stock

I have created animations in Animate CC. I use Adobe Media Encoder to convert to video using the adobe stock preset for H264 1080 without audio. However, All my videos that I upload via FTP to adobe stock as a contributer now have a yellow warning saying that the quality is too low. How do improve the quality? By the way I can upload .mov instead , but these are massive files - 480 MG as opposed to 5MG. What is the best practise to create a video from animate CC. Thankyou