I cant set my own Avatar

I am an Admin on a Server, and I have the same Group as every other Admin, but I can’t set my Avatar. If I select a file, there is no error; it’s just not set. I have the option to change my Avatar, but nothing changes after I chose the File I tried PNG, GIF, and JPG.
We have i_client_max_avatar_filesize on 999999 and also tested with i_client_max_avatar_filesize = -1

Yes everyone can upload his Avatar and its not only on this Server I cant apply an Avatar on any Server