When i click 'image' to open my file on the computer in Safari browser, nothing opens

I am using mac book pro and safari, when I try to add an image to my prezi, no files will open. Therefore, I am unable to add any images to my prezis. Can anybody suggest any way to fix this?

Hi Vanda , i 'm french and sorry for my english ;(  i could not succeed ,i changed the permissions but it’s the same problem, it doesn’t work. i am very disappointed because this function is very handy.
 I use Mac OS X, 10.10.5 et Safari 10.1 et Flash 
thanks for your little help

Having the exact same issue - we cannot currently upload anything into prezi