There are multiple reasons for the occurrence of the QuickBooks Won't Open issue. Most probably it happens due to using a corrupt QBWUSER.INI file or inappropriately installation of QuickBooks. No matter what causes the appearance of such an error, there are specific solving instructions you should go through. Here’s: · Make use of QuickBooks Diagnostic Tool to remove unnecessary files. · Rename the QBWUSER.ini file by opening the folder that contains this name and choosing rename tab. Once you rename this file by adding ‘old’ at the end, the problem can be fixed.