can't upload photo on presentation page mantra (newest version)

Hello, I wanted to change the lay out of my website https://www.mikevisserdrums.nl but after deleting a few photo’s I can’t upload the new photo’s.

I thought maybe because of a plugin that cause the problem so I have deleted most of the plugins and then did the update for the mantra theme (so now I have the latest version). Still not possible to upload photo’s.

the section ‘upload images’ completely isn’t working, I even can’t select a photo.

Hope you can help me to solve this problem so that my site will be online and update soon.

Thank you in advance! kind regards, Mike