What are you using as a sign of fermentation? An airlock bubbling is not a sign of one, a drop in the gravity from a hydrometer is. But yeast often needs 72 hours to grow enough to start working, it's called lag time and it is normal.
You don't do ANYTHING for 72 hours...then before you even consider pitching more yeast you take a reading.
Your airlock is not a fermentation gauge, it is a VALVE to release excess co2.
Fermentation is not always "dynamic," just because you don't SEE anything happening, doesn't mean that anything's wrong, and also doesn't mean that the yeast are still not working dilligantly away, doing what they've been doing for over 4,000 years....
The only way to truly know what is going on in your fermenter is with your hydrometer.
Like I said here in my blog, which I encourage you to read, Think evaluation before action
you sure as HELL wouldn't want a doctor to start cutting on you unless he used the proper diagnostic instuments like x-rays first, right? You wouldn't want him to just take a look in your eyes briefly and say "I'm cutting into your chest first thing in the morning." You would want them to use the right diagnostic tools
before the slice and dice, right? You'd cry malpractice, I would hope, if they didn't say they were sending you for an MRI and other things before going in....
It's the same with your beer, you don't preform a "cure" until you ascertain whether or not anything is wrong. And 99% of the time nothing is wrong.