Refused to apply style from 'https://captivateprime.adobe.com/app/%7B%7BserverThemeUrl%7D%7D' because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled. code example

put your .css file in a folder called public
in your app.js file add the following code:

app.use(express.static('public'));