No, probably not.
One possibility is that yeast tend to have a “lag phase”, during which they are acclimating themselves to the wort, taking in nutrients, and multiplying their numbers. It is not uncommon for it to take 24-48 hours for visible fermentation to appear, or even longer with cool-fermented lager yeast. This is especially true if you pitch liquid yeast cultures without propagating more yeast in a “yeast starter”. Liquid yeast packs often have very low numbers of cells by the time they get your home fridge because cells are dying off starting from the date of manufacture.
You may even see a layer of sediment form; this is normal. Rest assured that it is not all of your yeast.
The other possibility is that, if you don’t control the fermentation temp, you could have a runaway fermentation if the beer is kept at room temp. Fermentation creates heat and heat speeds up fermentation. Too much heat is considered undesirable. In a runaway fermentation, the fermentation can be over in the span of a few hours, such as when you are at work, at school, or otherwise occupied.
While only a gravity reading is definitive proof of fermentation (the gravity will be lower because sugar was fermented into alcohol, making the beer less dense) there are other clues, Look for clues such as foam or bubbling in the beer, a ring where the foam rose and then receded, increased cloudiness in the beer or churning, or a sharp sting to the nose from the CO2 if you place your nostril by the opening, crack it a bit, and take a deep sniff.
In any case, be sure to check the temperature of the beer (not ambient temp) and ensure that it is within the recommended range for your yeast
Courtesy – Reddit
