All CSS not working only in mobile?

[ILM]

This other thread has an other user having issues with css on safari mobile browser, maybe see if it is useful to you too:

iPhone Safari does not respond to max-width media query?

On reddit I was eventually told to just add a <meta name=“viewport” …> tag and then everything was fixed. It looks like there is a W3C working draft on the issue but it’s not a recommendation and neither Firefox nor Safari support the features: https://www.w3.org/TR/css-device-adapt-1/