While setting up a new Next.js project with Tailwind I ran into an issue.
This issue might just be a temporary issue due to configuration problems and libraries versions, but I’m writing this in case someone stumbles on it.
npm install tailwindcss postcss-preset-env postcss-flexbugs-fixes
In other words, PostCSS 8.1.13 was required but Next installed 8.1.7.
So I ran
npm install tailwindcss@latest postcss@latest postcss-preset-env postcss-flexbugs-fixes
and it worked!