You should run Get-PublicFolderMoveRequest rather than Get-MoveRequest to check if the move request is successful.
And then, you perform only one public folder move request at a time. You must use the Remove-PublicFolderMoveRequest cmdlet to remove the request after it's complete.
If you didn't remove the request, you will receive the same error.
And you need to remove the request, and then you can complete the second move request.
For more details: Move a public folder to a different public folder mailbox, Remove-PublicFolderMoveRequest, Migrate Public Folder to Office 365.