To fix any upload issue, we suggest the following options:
1. Please restart your computer and then try upload using our recommended Google chrome browser. If you don't have Chrome you can download it from the link below:
https://www.google.com/chrome/index.html
2. You can also try to batch resize the images to 3500 pixels in Adobe Photoshop or similar software before upload. The uploader will then skip the resizing and simply upload the file directly.
You can view our batch resize guide at the link below:
http://helpdesk.onlinepictureproof.com/knowledge_base/topics/batch-resize-pictures