Recently I faced the QuickBooks Error 6073 on my system, and the reason behind this issue was that my company file was being accessed in the single-user mode, on another device. On contacting an expert, this is what I found to be useful in eliminating this issue-
Close QuickBooks files and folders on all the systems.
Login in the Host computer.
Open the company file here.
Click the File tab.
Choose the Switch to Multi-user option to check if the error has been resolved.
If the error persists, you must restart all connected devices.
To learn more about this along with other solutions, read here. You can also get in touch with the expert team at 855-856-0042 for swift assistance.