I appreciate the troubleshooting steps you've tried, gate.
There are possible reasons why this issue can occur.
Your company name may be too long
You may have a damaged or missing QBWUSER.INI file
You may have corruption on your hard drive
Your program files or QuickBooks Desktop installation may be damaged
You may have a damaged Windows operating system
Since running the QB Tool Kit didn't work, let's proceed to rename the QBWUSER.ini file. Please be reminded that renaming it will erase the list of your previously opened company files and may need you to re-open it manually. Here's how to rename the file:
Open the folder where the QBWUSER.ini file is saved: \Users\[Your user name]\AppData\Local\Intuit\QuickBooks [year] If you can't see the folder, you might need to enable hidden files and folders.
Right-click the QBWUSER.ini file and select Rename.
Add .old at the end of the file name (as in QBWUSER.ini.old).
If it works, try opening a sample company file. If you can open it, copy your file to a different folder. Open it from the new location. If you're able to open your file, then the problem might be a damaged folder or folder permissions.