maybe it's a tailwind problem?

It would help to see, your css files, your tailwind config file (if using tailwind) and your package.json so we can see what versions you have installed. I;m guessing most likely you have also upagrded to tailwind v4 and not set up the new config file correctly.

you can easily use the setup tool from tailwind to migrate from v3 to v4 btw

it will auto update the css file, config and dependencies