Applying for a visa is no simple task, it cab be very complicated. You need to make sure that you are using the correct form. The forms change from month to month so there is a real possibility that you may have used the wrong form.
The visa application charges are also subject to change. If you pay the wrong fee, then you may have made an invalid application and you may not be granted a visa. The visa application charges are very high. If you apply for a visa and the application is refused, there is no refund of your visa application charge.
One must also ensure that all of the questions have been answered on the form. If you do not answer all of the questions on the form, then the Department of Immigration may treat the application as being an invalid application, and once again, your visa may not be granted.
It should also be noted that if you apply for a visa, the application process may take a long time. In some cases the application process could take up to a year and a half.
If you already have a visa and you want to apply for another visa, then make sure that you apply for the new visa before your current visa expires. If you visa has expired then you may not be able to apply for another visa. It is therefore essential that you apply for your new visa before your current visa expires.