Hi !
When you attempt to move the items to your new shop are you getting any type of error?
Which browser are you using?
Can you note the steps you have taken before getting this error?
Thank you for the information, !
Not sure exactly why you're getting the message, since it sounds like you're following the correct steps. I'm wondering if it has to do with it trying to load an old page/from old cookies. Have you tried clearing your cache and browsing cookies and then attempting?