Keith, in all likelihood, the yeast itself is dead. This is not
uncommon these days because very few shops are willing to pay the
extra cost to have their yeast shipped to them refrigerated. A lot of
the yeast shipped on the hottest days of last summer simply died in
shipment, when the cargo compartments of the trucks they were
delivered in reached temperatures in excess of 110 degrees. Most wine
yeast dies at 105 degrees F. Also, the yeast may simply have been too
old when you bought it. Check the sachets to see if they have an
expiration date printed on them.
If you get in the habit of activating your yeast in a starter solution
(see the last section on page
http://winemaking.jackkeller.net/yeast.asp), you will know within
hours whether a sachet of yeast is good or dead and this will save you
four days of waiting and wondering. Activate a new sachet as
instructed. If it too is bad, then you need to get new yeast.
Good luck and Happy Easter.
Jack Keller, The Winemaking Home Page