Error: 80040435 (Unknown error) : Recent changes to your configuration require you (the QuickBooks Administrator) to go into the Integrated Applications preferences and re-authorize your integrated application to log in automatically
This error message is a bit of a misnomer and typically means another QuickBooks user is connected to the company file in Single User Mode, preventing any other users or integrated application from connecting.
Verify the Boomi Atom is authorized to connect to QuickBooks automatically. Log into the QuickBooks company file that the QuickBooks Connection is attempting to connect to and go to Edit > Preferences > Integration Applications > Company Preferences, select the Atom's application name and click Properties. Verify the integrated application is allowed to connect automatically. If not, check the box, click OK, and retry the Process.
If the integration application is allowed to connect automatically, this error can also mean another user is logged into QuickBooks in "Single User Mode", which effectively puts a lock on the company file and prevents the Atom (or any other user) from accessing the company file. Make sure all other users are connected to QuickBooks in "Multi-user Mode" (this can be toggled in QuickBooks under the File menu) and retry the integration.
It is understood some QuickBooks administrative functions can only be performed in Single User Mode so be aware that the integration will not work during those times. When the administrative work is complete, you should switch back to Multi-User Mode and the integration will pick up where it left off.