If you are using Tailwind Css classes inside svelte variables, they will work on the REPL since it's using tailwindcss JIT, but they won't work inside the page for the compiled css, the classes need to be safelisted in tailwindcss config.
When saving the component we do the safelisting automatically after compiling svelte component, but we extract the classes from the HTML, not the variable names.
To fix the issue at the moment, try to write a single element (example "div" with hidden style) and provide all the possible classes. This will allow Fouita to generate the css used for your project with the classes safelisted.
content properties inside tailwind config won't work, they are used internally for building the css.
Let me know if that works for you, otherwise you can send an email with your project link to firstname.lastname@example.org and we will take a look for you.