If you are setting up your company data file with the intent for using multi-user access, there are specific steps that you or your IT team need to follow. The following link leads to a knowledge base article on Intuit’s website that contains all the steps necessary to set up a company file for hosting for multi-user access:

https://community.intuit.com/articles/1502075-host-your-company-data-file-in-multi-user-mode

Additionally, the FM Books Connector requires certain steps to ensure proper communication with the Company File:

1) The initial connection must be performed with QuickBooks open on the client machine, with the company file opened in QuickBooks, in Single User Mode with “Admin” access
2) When beginning a session to QuickBooks, the “ShareMode” parameter must be either blank (””), or “Multi”. A parameter of blank tells the plug-in that it does not matter what share mode to use (either “Single” or “Multi”)
3) If communicating with QuickBooks company data file with the application closed, a valid file path to the company file must be provided to the PCQB_BeginSession function

Detailed information about communicating with QuickBooks via the FM Books Connector can be found in the Developer’s Guide.