Issue:
Unable to integrate Web TimeSheet with QuickBooks Enterprise edition after upgrading QuickBooks to version 12. When the user tries to open the company file the following error message shows up:

Error opening your company file.

Cause:
This issue occurs because the QuickBooks company file is not updated to the latest version after the QuickBooks upgrade.

Resolution:
Convert the QuickBooks company data file to the latest installed version of QuickBooks.

Open the new version of QuickBooks.
Choose File from the top menu and then click on Open or Restore Company.
Click Open a company file and then click Next.
Browse to your data file, select it, and click Open.
If QuickBooks displays the Move Company File window, read and follow the instructions shown there.
Read the information in the Update Company File for New Version window, enable by putting a check mark in the box to show you understand, and click Update Now.
Follow the instructions to back up your company file, and make a note of where you put it, in case you need to refer to it later.
When the message You are about to open a company file using a newer version of QuickBooks. Do you want to continue? appears, click Yes.
Once the company file is updated to the new version, launch Web Timesheet Integration Manager for QuickBooks and continue with the Integration.

Note:
Once the company file is updated, it is recommended to store the backup in a safe location. For any future reference.