This happens when the application you want to add has an existing Owner ID on QuickBooks.
What you can do?
To fix this, you need to remove the existing Owner ID.
1. Download the CP3 tool, https://intuit.app.box.com/s/obblc4bcxbolrim1qmxjdbbhqlf9rbbv then select Open.
2. Select - Select file, then search for your QWC file. This puts the file in the Enter QBWC file Location.
3. Select Open, then Remove Stamp.
4. On the QuickBooks Application Certificate window, select Yes, then Continue.
5. On the Access Confirmation window, select Done.
6. Follow the instructions, then select OK.
7. You should get a confirmation that the Owner ID was removed. Select OK.
8. Exit and reopen QuickBooks and Web Connector, then re-add your third-party application.