Has your QuickBooks "Admin" user password changed recently? If so, this unfortunately breaks the automated syncs within OpenSync. To address this, you must re-authenticate the OpenSync app with QuickBooks. To do so, follow the steps below:
Remove Current OpenSync Authentication From QB
-Login to the device where the OpenSync application is installed. (Please be sure to login as the same domain user that was used to initially configure it.)
-Login to QuickBooks in Single User mode using the "Admin" user.
-Click on "Edit" in the menu bar.
-Select "Preferences" from the Edit menu. (This will bring up the window below.)
1) On the left hand pane, select "Integrated Applications".
2) At the top, select "Company Preferences".
3) In the center, select "OpenSync" from the application list.
4) With Open Sync selected, click "Remove".
5) Click "OK" to save changes.
Re-Authenticating OpenSync For QB
Once you remove the OpenSync app authentication from QB, it is now time to re-authenticate it.
-With QB still open and logged in as "Admin" in Single User mode (under the same domain user), launch the "OpenSync" application using the desktop icon.
-Once OpenSync launches, ensure that the service is stopped as outlined in the image below. To reach the OpenSync screen below, click on the highest level branch on the left hand side titled "OpenSync" (#1 Below). Once on the screen, if the service is not stopped, it can manually be stopped using the "Stop" button (#2 Below).
-From the left hand pane, under "Tasks" right click on the task titled "PLDETAILYTD" and select "Run". (This will bring up the window below in QB.)
1) Click on the option that sates "Yes, always allow access even if QuickBooks is not running."
2) Select the "Admin" user from the dropdown.
3) Click on "Continue. (Then confirm the changes and click "Done" on the next prompt.)
Once you have re-authenticated the OpenSync app, you can now put QB back into multi-user mode and schedule the machine for a reboot to kick off the task the task in Task Scheduler and launch the app in the background.