Strange WordPress Issue

Recently my site started to receive more traffic so I decided to move it to a different server. I wanted to use apache + nginx (to serve static files). For some reason I can’t view the post editor on this new server although everything appears to be fine on the main page. I tried different kind of web servers (litespeed) but the same thing happens.

I will post a screenshot below:

https://snag.gy/3WBZx.jpg <– visual post editor issue

Also, you can see the left sidebar color is black. On the working version the sidebar is grey.

Any ideas please? I simply don’t understand what causes this.