Images not uploading to Course presentation or Hotspot image activity

Today, we discovered that all of a sudden we can't upload an image saved as JPG or PNG into a slide in Course presentation or into a Hotspot image tool. An error message 'File type isn't allowed' pops up when I try to upload the image. However, this issue doesn't happen for an image saved as JPG HD. We are not able to save every image as JPG HD however.