Why my submit button is Grayed out

If your images in the "New" tab are displaying a red dot, it means that you haven't added all the necessary info prior to submitting. Once you've done that, the dot will change to green and they'll be ready for submission, unless you've reached your submission limit for the week, in which case, the Submit button will remain grayed out.

Because you've reached your submission limit for the week. Wait until some assets get reviewed.