Hi, I am here to provide the reason why QuickBooks not opening. This is a common problem that every user faces or might face in the future as this can happen due to damaged or corrupted files. It can also happen if you are using the wrong method or username password to open the QuickBooks. If the file is opened in another system this can also be a possible cause for the file not opening. It is better to check all dynamics related to it before going to a technical expert.