timer_tick event

Well, I don't know what your code looks like because you have not shown it here.  The first thing to check would be whether or not the timer control has been enabled.  By default, the timer is disabled.

For example, if you had a splash screen and you wanted to display it for five seconds, you could drop a timer control onto the splash screen, set its interval property to 5000 and, in the tick event handler hide or dispose of the splash screen.  In the form constructor, you could set the timer control's enabled property to true.  If you have enabled the timer you will need to look at the timer control's tick event handler to see why it is not getting fired; you can do that by putting a break point inside the event handler and stepping through it.

Example:

public frmSplash()
{
     InitializeComponent();
     timer1.Enabled = true;
}