This problem occurs while you are trying to convert the database which contains same name for multiple categories or Locations.
In the 1.x, 2.x or 3.x versions, Paper Tiger would allow the same name for the multiple Categories or Locations. This results ambiguity in finding the proper location and categories. To avoid that ambiguity, in the latest versions it is not possible to have the same name for multiple locations or categories.
You need to change the Category names or Location names, so that they will be unique.
If you have your old version of Paper Tiger running (1.X, 2.X, or 3.X), you can open up the Database in the old Paper Tiger version and change the location names manually. Once you have changed the names, you can save a backup of your database and convert it successfully in the NEW version of Paper Tiger.
If your old version of Paper Tiger is not accessible, please open up a support ticket and send us your old Paper Tiger database and we will convert it for you. You can open up a new ticket here, or click the Open Support Request on this page: