Having trouble embedding snippet code onto a selected page.
What code snippet are you trying to add to your page?
The label of the code is on the new tool page but the embed is not displayed.
Do you mean that the code snippet is still shown and the intended image or form is not showing for example?
If you are trying to add something to an html iframe on your page like a piece of html code from a third party then you can simply follow this page here and read about the limitations too.
https://support.wix.com/en/article/using-iframes-to-display-visible-content-on-your-site
https://support.wix.com/en/article/embedding-custom-code-to-your-site