Air lock activity or lack of it often appears on the forums. However it is only 1 piece of evidence to indicate the brew is fermenting.
As stated before, there are countless reasons why the airlock might not bubble, yet fermentation is happily traveling along.
Age and type of yeast make a big difference as does how is has been stored and prepared. Higher brew temps can make the yeast more active, conversely a low temp means activity will be slower
The trick here is in the method. Never base your theory on just 1 piece of evidence. Unfortunately kits always put that in the instructions. I guess they don't want to frighten people away by making it sound like you have to be measuring and testing all the time. temperature, airlock activity, grav readings, taste and smell can all tell you how the brew is doing. If you have the chance to see a ferment in a clear glass carboy, you'll also see how much activity there is in the liquid when the yeast is active. This really cant be seen in a plastic fermenter.
Certainly watch the airlock and its extremely soothing gloop gloop sound.
Give the fermenter a few days and then take a sample and see if the reading has dropped a few points
If the reading hasn't changed much then it may be time to take action
after a while you'll get to know through experience how your brew is going and when there is a problem
in the mean time relax and have a home brew, or an appropriate substitute.
On a side note, I've become extremely lazy with my fermenting. I tend to brew the same each time and have done for some time I've got a pretty good idea how the ferment is going so I haven't actually taken a hydrometer reading for quite a long time. I do keg rather than bottle so that gives me a little lee-way as I don't need to worry too much about bottle bombs. I just make sure the sanitize routine is OK, the temp control is good and look after the yeast. I know its dry in the kits but try and make sure it stays in a cool place while your not using it because it will be much healthier when it comes time for it to go to work.
:blink: end rant
BTW - happy brewing - once you get to the final product, all your worries will be distant memories