Beer brewing question?

The time it takes between pitching the yeast and the beginning of active fermentation is called lag time. Lag time can last up to 72 hours and depends on many factors. The biggest factor is the health of the yeast cells you pitched and how many you pitched. It takes hundreds of billions of yeast cells to properly ferment a typical 5 gallon batch of beer.

Another very big factor is the amount of oxygen in the wort. Yeast require oxygen to rapidly reproduce (they can reproduce without oxygen, but it is much slower). If you haven't already done something to introduce oxygen into your wort you could shake the container vigorously for several minutes. Once active fermentation has started DO NOT introduce oxygen into your wort, it will cause oxidation and your beer will gradually taste more and more like wet cardboard.

Other than that I wouldn't worry about it. Unless you killed the yeast by putting them into wort above 110f they are in there and even if there aren't as many as there should have been they will start doing what they do best, eating sugar and producing alcohol and CO2. Some beers have a very large krausen (the foam) and some have minimal krausen. Some take a day or two to produce a krausen and some have a krausen in a few hours. Looking at your beer is not the best way to determine if it's doing what it should. Wait several days and take a hydrometer reading and compare it to the reading you took before pitching the yeast (you did take an O.G. reading, right?).

Good luck and happy brewing.

Did you remember the yeast and sugar. Is it warm enough?