Why is the mobile preview not showing in my mobile devices?

If this is just an issue within the Wix Editor then you should be going through Wix Support as it is not a code related issue.
https://support.wix.com/en/about-wix/contacting-wix-support

You can go back in site history to a previous saved version and check again.
https://support.wix.com/en/article/restoring-a-saved-version-of-your-site
https://support.wix.com/en/article/viewing-and-managing-your-site-history