First,
and foremost fermentation can take up to 72 hours for the yeasties to start, it's called lag time.
https://www.homebrewtalk.com/f39/fermentation-can-take-24-72-hrs-show-visible-signs-43635/
But by visible signs they DON'T mean airlock activity.
Your airlock is not a fermentation gauge, it is a VALVE to release excess co2.
If your airlock was bubbling and stopped---It doesn't mean fermentation has stopped.
If you airlock isn't bubbling, it doesn't mean your fermentation hasn't started....
If your airlock starts bubbling, it really doesn't matter.
If your airlock NEVER bubbles, it doesn't mean anything is wrong or right.
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 "doing anything" without taking a hydrometer reading is tantamount to the doctor deciding to cut you open without running any diagnostic tests....Taking one look at you and saying, "Yeah I'm going in." You would really want the doctor to use all means to properly diagnose what's going on. It's exactly the same thing when you try to go by airlock....And that means pitching more yeast.
Wait til it's been 72 hours and check gravity before you do anything.
Bobby M recently did a test on year old stored yeast here;
https://www.homebrewtalk.com/f13/testing-limits-yeast-viability-126707/
And my LHBS cells outdated tubes and packs of yeast
dirt cheap 2-3 dollars each and I usually grab a couple tubes of belgian or other interesting yeast when I am there and shove it in my fridge.
and I have never had a problem with one of those tubes. I usually make a starter but I once pitched a year old tube of Belgian High Gravity yeast directly into a 2.5 gallon batch of a Belgian Dark Strong, and after about 4 days it took off beautifully.
Same with jarred yeast.
With any stored, old yeast you just need first to apply the "sniff test" if it smell bad, especially if it smells like week old gorilla poop in a diaper left on the side of the road in the heat of summer.
Then make a starter, and if it takes off you are fine. The purpose of a starter is to reproduce any viable cells in a batch of yeast....that;s how we can grow a starter form the dregs in a bottle of beer incrementally...and that beer may be months old.
Even if you have a few still living cells, you can grow them....That's how we can harvest a huge starter (incrementally) from the dregs in a bottle of some commercial beers. You take those few living cells and grow them into more.
If yeast can be grown from a tiny amount that has been encased in amber for 45 million years,
45 million year old yeast ferments amber ale we really don't need to sweat too much about yeast viability....
we just need to think in terms of making starters. Viability isn't really an issue if you are reproducing a lot of healthy cells. Which is what you are doing when you make a starter.....
Since it appears you didn't make a starter you will have lag time, probably even longer than the 72 hours we talk about here.
If you are interested, read this as well,
Why the idea of "dead yeast" is mostly bunk.
relax
