According to Intuit, Error Code -6073, -816: “QuickBooks is unable to open this company file” is an error that has multiple possible causes. The possible causes include:
- multiple computers have hosting turned on instead of only 1
- different releases of QuickBooks on the server and the affected workstation
- insufficient file permissions
- the Database Manager service is not running
- the network data file (.nd) is damaged, missing, or marked as hidden
- the transaction log file (.tlg) is marked as hidden
- security software (e. g., a firewall) is blocking network traffic
- other software is currently scanning the QuickBooks company file
- QuickBooks is attempting to run a scheduled backup while the company file is in use
- the company file (.qbw) is damaged
A screenshot of the actual error appears below:
There are a number of troubleshooting steps to resolve this error that are discussed in detail in the Intuit knowledge base article linked below. Before proceeding to those steps, insure that all computers in your QuickBooks installation have been updated to the latest QuickBooks release. To verify the version and release of QuickBooks, press F2 while QuickBooks is running to display the Product Information window. The Product field shows the version and release at the top left of the window. In the example below, Premier Accountant Edition 2009 is the version and R3P is the release. Complete this step on each computer in your multiuser setup.
To follow the troubleshooting steps to resolve Error Code -6073, -816, consult this Intuit knowledge base article.
[Update: Unfortunately, it appears Intuit has removed that article, so the link is dead.]