QuickBooks is unable to open this company file. It may have been opened by another user. You should ask that user to switch to multi-user mode so you can both use the company file at the same time. The file could also be located in a read-only network folder. If it is, ask your system administrator to make the file accessible.
Error codes: (-6073, -99001)
This error means that someone has the company file opened in single-user mode. Have that user switch to multi-user mode. If necessary the server Admin can end all QuickBooks sessions via the Task Manager.