XF 2.0 Can't highlight text in editor

[AndrewSimm]

I can't highlight text in my editor. It still functions of highlight (can copy), but it's not visible.

Here is what it looks like when it works on xenforo's website.

 

[AndrewSimm]

The issue turned out to be CSS related.

 

[GeekyPhilip]

I have the same issue and I have not changed the CSS, how did you fix yours?