QBWC error codes in QuickBooks Desktop: what they mean and how to fix them
QuickBooks Desktop users see QBWC codes when the Web Connector fails; here is what each common error means and how to clear it.

QuickBooks Desktop users who sync with a third-party app through the Web Connector have been turning up with a familiar set of QBWC error codes. The codes are not all the same problem. Some point to a permissions issue in Windows, some to QuickBooks itself, and one to the server run by the app provider. The fixes are short once you know which code means what.
QBWC1005 and QBWC1006: file and log access
QBWC1005 appears when the Web Connector cannot create a file it needs to run. The standard fix is to make sure the Windows account that starts QuickBooks has write access to the Web Connector folder. If you normally open QuickBooks under one account and the connector under another, switch to the same account for both and try again.
QBWC1006 is the same family, but the missing file is the log file, QWCLog.txt. The connector either cannot locate it or Windows has marked it read-only. Open File Explorer and go to this folder:
%LOCALAPPDATA%\Intuit QuickBooks Web Connector
Inside you will see a version-numbered folder. Open the newest one, find QWCLog.txt, right-click it, and choose Properties. Clear the Read-only box, then confirm the current Windows user has full control. Close the Web Connector and open it again to test.
QBWC1007, QBWC1008, and QBWC1009: connection failed
These three codes all mean the Web Connector found QuickBooks but could not reach it. The usual cause is one of three things: QuickBooks is not running, no company file is open, or an open window is blocking the connection.
Exit QuickBooks completely, reopen it, and sign in to your company file. Close any open windows, dialogs, or reports before you try the update again. A clear desktop is usually enough to clear the error.
QBWC1011: application is not registered
QBWC1011 says the application named in the error does not exist in the Windows registry. That is a good sign the third-party app did not finish installing. Close every Web Connector window, then exit and reopen the connector.
If the application still does not appear, you need its .QWC file. That small file is the connection definition for the app, and your app provider supplies it. Download the .QWC file to your computer, then add it through the Web Connector’s add-application option. After that, the app should show up in the list.
QBWC1012: the app server rejected the request
QBWC1012 carries a longer message about authentication coming back with a server-side processing error. That server belongs to the third-party app, not to QuickBooks. The failure is on the provider’s side, and there is no local fix.
Contact the app supplier and describe the error code. They are the ones who can check their service and the authentication handshake. Intuit cannot resolve this one from your machine.
QBWC1016 and QBWC1018: nothing selected, nothing loaded
QBWC1016 appears when you click an update option before selecting an application. In the Web Connector window, click the row for the app you want to update, then choose Update Selected instead of a general update.
QBWC1018 appears when no application is available to select at all. That means no .QWC file has been loaded into the connector yet. Obtain the file from your app provider, add it, and the selection list will populate.
If the same code keeps coming back
When a QBWC code refuses to clear, start with the .QWC file. A stale or partially saved file explains many of the repeat failures. Re-download the file and add it again. If the error is still there, the next step is the third-party app’s support channel, because several of these codes are about the app’s server and not about QuickBooks Desktop itself.