There are a number of things you can trouble shoot with. 1st is the most basic, go through your admin/images and admin/preferences to make sure you have the correct settings for images and uploads.
Next, if you installed the plugin via the admin upload, then uninstall it and use FTP (always use ftp for plugins and theme uploads).
Next check your admin cpanel/images and make sure you do not have an error for GD2. (if you do then you need to have your host reconfigure Apache - which is easy two clicks and a 3 minutes to do) if you have WHM (dedicated server) then go to [link]
you should get warnings in e107 if it is a chmod issue, but you can still toggle 755 to 777 for the images folder.
also, go to your admin cpanel/file inspector and run a scan and then do the same in databases to look for error files, make sure to scan plugin database.