If you are getting error code 80040408 while running QuickBooks or while opening the company file, then this indicates installation errors and company file issues. Down-below listed is a sure shot method that you can implement to get rid of the error without using any other method that involves Windows troubleshooting.
Run QuickBooks Clean Install Tool to Reinstall QuickBooks
NOTE: Before reinstalling QuickBooks make sure to create a backup of your company file data to avoid data loss.
Download QuickBooks Tool Hub from the QuickBooks website.
Open the downloaded file from the downloads of your computer and proceed with the installation.
Agree to the terms and conditions and get the app installed.
After the installation open the application from the desktop of your computer and click the Installation Issues tab.
Click QuickBooks Clean Install Tool to reinstall QuickBooks.
Try to run QuickBooks and open company file in it to check if the error is resolved.
In rare instances, you might still face QuickBooks error 80040408 even after reinstalling QuickBooks and in such cases you can dial (844)-932-1139 to seek direct help from certified QuickBooks experts.