When I went to add an image, I selected the image and clicked to upload.
I received this error:

You Do Not Have Sufficient Permission To Write To Folder Users/255/01/-1/. Please Contact Your Hosting Provider To Ensure The Appropriate Security Settings Have Been Enabled On The Server.

That probably means that there is a file permission error in the folder. It is an operating system issue. All of the folders in DotNetNuke's web directory need to grant full permissions to the IIS "worker task."