When QuickBooks won't open even after the command has been given,

one of these reasons is considered to be the root of the problem .Look at this.

Because of its deterioration,the system's hard disc cannot support opening such large software programmes as QuickBooks.
The data file's name is either unnecessarily long or contains unusual characters.
The operating system does not operate in parallel .
The installation of QuickBooks was defective.
The product registration for QBWUSER.INI file is damaged.