Hello, DDCC. 

Let me share troubleshooting steps to help you get rid of the error you've encountered. 

QuickBooks error -6190 -816 is defined as QuickBooks was unable to open the file on the host computer. That implies that the file is not accessible. Also, this error is a consequence of when more than one user tries to access the company file.  

Also, there are several reasons why QuickBooks error 6190,816 could occur. Few of them are: 

• The transaction log file does not match with the company file 
• Single User Mode 
• Data Corruption 

To fix the error. Try out the following methods to eliminate error -6190 ,816 from QuickBooks: 

1. Update QuickBooks, If you are facing the QuickBooks error 6190, make sure that the QuickBooks software is updated with the latest version.  

2. Rename the File 

Make sure that you are using the computer in which the company file was saved. Then, you have to rename the files. It won’t cause any data loss. You can rename the file through the following steps:

• Open the company folder
• The transaction log file and company file will have the same name but different extensions. For example, company file will be named as [company file name].qbw.nd and a transaction log file will be named as [company file name].qbw.tlg. You need to identify the company file out of those two. That is the only tricky part in renaming the file
• Once found, right-click the company file and select “Rename” option. Enter any new name or simply add “-OLD” at the end of the name
• Make sure that you don’t delete extension or “.qbw.nd” from the end
• Same way, rename the transaction log file without omitting the extension
• Exit the system now
• Open QuickBooks and try to login in the company file                                                                                                                                                                                                 

     3. Single Mode User Check 

As mentioned before, if any user is accessing the company file in single mode, you could receive Error -6190. To avoid that follow the listed steps:

Make sure all the users are logged out of the QuickBooks Data file.

• Then, restart the computers
• Now copy the data file to the desktop or another location apart from its source
• Again copy the data file back to its original location
• Sign in to QuickBooks 

    4. Update Windows

Updates prevent and often fix install errors and more. To update:

• Update the Window
• Restart your computer once the updates finish
• Install QuickBooks Desktop again 

You can also check out this article for more troubleshooting steps about the error -6190,816: Resolve Error -6190,816. 

I'd also suggest giving us a call so one of our Technical Support specialists can guide you through the process. Here's how to get in touch with our QuickBooks Desktop Customer Care: 

1. Open QuickBooks.
2. Go to the Help menu, then select QuickBooks Desktop Help.
3. Enter any keyword, then press Enter.
4. Click Contact Us at the bottom.
5. Enter "Error 6190,816" in the description box.
6. Select Let's talk or Continue, then choose Start a chat or Get a callback. 

Don't hesitate to visit us again here if you have any other concerns or follow-up questions. The Community always has your back.