No invitation to an interview: This could be the reason if the application is followed by a rejection. Bad timing is one of the most common reasons for unsolicited applications.
A salary expectation that is too low and does not match your qualifications could also cause HR managers to reject the application. If the company is about to sign a contract with another candidate, it is likely that your application will no longer be considered for the position. The application process may be very advanced when you submit your documents.