This is really strange. I set up a website as a network (the other sites of the network are temporarily in maintenance mode).
I upload Montezuma theme. I'd like to have all title (header title, widget title, post title) in one color so I read some threads in this forum and I went to the administration menu of montezuma's css files.
As soon as I click (without change or save anything) a css file menu and widget icons disappear.
A solution is to re-upload every time the style.css file and the javascript file that I have in wp-content/uploads/montezuma.
Do you know how to find a solution to this problem?
Thank you!

As soon as I click (without change or save anything) a css file menu and widget icons disappear.

can you be more clear, do the icons disapear in the front end or backend?
where do they disapear?

They disappear on front end. An example could be the stars above the menu Home - Chi siamo - etc., as soon as I click on any css file in montezuma options they disappear, so I have the "Home Menu" without the stars.

But I'm seeing the stars on your site

I found the solution here