There are plenty of reasons due to which QuickBooks Not Opening issue is been faced by the many users. This generally happens if the company files get corrupted or damaged, the file may be opened on another system or the QuickBooks application gets outdated. Whatever the cause could be, the error will definitely be resolved at an instant. To fix it, you are just required to supress the QuickBooks Desktop application. If this doesn’t effective in opening the QuickBooks freely, you can run the QuickBooks Install Diagnostic Tool on your PC as it detects the error and troubleshoot instantly if finding any.