Cannot Add Images TO upload a Banner

I have a mishap with the WP theme on my website…After testing though I do not think it’s the theme, I think it’s WP. It would not let me upload a banner image to the site…The “add new image” button is not even loading an up-loader. I tried updating WP, and first thought that was the issue, but I have the same theme on other websites, and it is working fine on others…I also tried activating other various themes on there and am getting the same issue. So, I figured out it’s not the theme, it’s some error with the site…I am wondering if you could spent a little time trouble shooting to see if there is some other error on that site, so I can fix this issue as well as others I have been having on there? Thanks so much!