Side arrows in testimonials disappeared + warning

I noticed that the 2 side arrows in the testimonial section are disappeared ( www.adottareunmaggiorenne.it )
It is still possible to localize their position moving over the mouse (and they work), but they do not appear at all.
I had previously changed their color from dark to light because of the dark background (files "prev.png" and "next.png").
I put back the original files without any change.

Moreover, a message about a "function ckLoadEditionPopup missing" appeared, warning me to inform the developer (see attached screenshot)

What to do to get back those arrows?

Hi
for the images, go in the Page Builder CK options and disable the CSS compilation. Tell me if it works
for the popup and message, on your screenshot we see that you have lost your session and needed to log again. This is probably the problem
CEd

It worked! Thank you!