HTTP error on Upload

On my WPMU DEV hosted site, when I try to upload some images it returns this error https://cdn.livechat-static.com/api/file/v2/lc/att-old/8801096/f8a01d8e9fe396ed075f104a9e678655/Screen%20Shot%202019-09-04%20at%2010.41.48%20AM.png

Can you help me?