QuickBooks Won’t Open Error is an error that restricts the user from opening the QB desktop software. Due to this error users are unable to access the QuickBooks component, company files and also restrict users to access the advanced feature.
There are many reasons for Quickbooks won't open errors like

The qb company name could be very long.
The error occurs if the hard drive you are using is corrupted.
Incorrect installation of QuickBooks Desktop.
The QBWUSER.INI file could be damaged.
The operating system could be outdated.

We can resolve this error by just following these simple steps
Shut down the QBW32.exe process
Rename the QBWUSER.ini. file
Repair QuickBooks Desktop
Restart the Desktop
QuickBooks Install Diagnostic Tool