File manager doesn't open anymore

My file manager doesn't open at all. It worked fine a few days ago, and everything on the site itself works fine, nothing is slow and my cache is empty.
But as soon as I try to place a new picture of access the file manager, the window opens but it's white and no matter how lang I wait, nothing happens.
This is frustrating, it started yesterday and is still the same way today.
I also wrote an email to the yola help, but no answer yet.