Add items to the list not working

Hello!

Looking forward to using the plugin! However, after installing and activating it, when I try to use it from a new post, the copy function takes me to the main screen of Multisite Content Copier. When stepping through copying from thee, I can only get to step 3. I select the new post that was created by clicking the checkbox next to it and click "Add items to the list" button, and only get an error message stating that: "You must add at least one item to the list".