Adoba Animate 2018 sprite sheet only one image

Disclaimer: Probably bad english and animate noob (first animation)

I am trying to make a simple 1 second animation and put it in a psritesheet

My problem is when I do "create spritesheet" it shows only one image and the symbols are not in the right place in the spritesheet preview

I did the animation using motion tweens, I tried converting it in a image by image animation, I tried copying it and pasting it in a new symbol (select everything, insert, new symbol, paste in timeline) and it still doesn't work... Help?

Sorry the screenshots are in french!

I know there's a bunch of unused symbols, trying to learn the software!

Thanks for your time!