First, 21 hours is NOT 72 hours, and as we say here, http://www.homebrewtalk.com/f39/fermentation-can-take-24-72-hrs-show-visible-signs-43635/
(But in thise thread it is said repeatedly Airlock is NOT the visible sign we are talking about.
) THEN take a hydrometer reading, and you will know what your beer is doing.
By "not active at all" are you referring to airlock activity? That's never an accurate indication of fermentation. It is a vent to release excess co2..not a fermentation gauge...
Your beer will ferment whether or not the airlock bubbles. If it's not bubbling it usually just means that doesn't need to release any 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....
Thinking about adding more yeast, like you asked about, without first taking a grav reading is tantamount to the doctor doing the same thing to you....proposing a "cure" without really knowing what the problem is.
annasdadhockey... You could have handeled this yourself.
if in doubt, just quote one of the 10,000 posts whre I have said the same thing..I don't care if you take my words as gospel and not credit me..you knew the answer.
you couolda said it yourself.....