Quickbooks Error 6123 is a message that users are receiving when they try to open their company file. This message can mean that Quickbooks has run into a problem with the company file and cannot open it. There are a few ways to fix this issue. The first step is to ensure that the server is up and running. The second step is to ensure that the user has administrator privileges on their computer and in Quickbooks. The last step is to try opening the file again.