For starters,
if
isn't a loop - it's a conditional, it's only executed once and can't "loop back" on itself.
Second, you don't enable timer2 at all!
Third, that's some odd code, given that you disable the timer as the first thing you do when it gets it's tick event - which means it won't give a second tick unless your enable it again, which you don't.
Scrap that, are start again.
Instead of having two times, have one, and instead of keeping a minutes and seconds count, use a "target" DateTime value:
private DateTime countdownTarget;
...
countdownTarget = DateTime.Now.AddSeconds(60 + (30 * 60));
myTimer.Start();
Then, in your Tick handler check the target:
TimeSpan diff = countdownTarget - DateTime.Now;
int secs = diff.Seconds;
int mins = diff.Minutes;
if (diff.TotalSeconds <= 0)
{
countdownTarget = DateTime.Now.AddSeconds(60 + (30 * 60));
}
You can then use the the two values to set your labels.