button works in imagemagick directory path

Hi I,m Newbie here ..
I have problem with buttuon works in imamagick directory path.
I have install imagemagick in my server Ubuntu, but button to test it, doesn't appear. it is totally blank.

what's should i do?

thanks

Are you saying there's just no "Test" button in the Site Settings panel?

Have you tried using a different browser?

I have try it ...
because the main problem is, when I input logo header from admin panel or from configure theme, i can't remove back from there, so i must go to image directory to remove from them.

I don't know what the problem, i have try to reinstalls omeka with LAMP server in UBUNTU, it's came back with their problem.