I can’t see the add to cart button on my mobile on my site composelimited.com nor can I see it on wix mobile editor??
If you are talking about the Wix Stores Add To Cart button like this here.
https://support.wix.com/en/article/adding-a-standalone-add-to-cart-button
Then you are better suited contacting Wix Support for more help with the issue with the Wix Stores app.
https://support.wix.com/en/article/contacting-wix-support
In the meanwhile, use ‘Layers’ from your Wix Editor to see if you can find it on each of your desktop and mobile editor versions. https://support.wix.com/en/article/using-the-layers-panel