This is indeed my third brew, and the first where I have made attempts to control the temperature (partially submerged fermenter and cold wet towell wrapped around it). Temp has not been above 24c, have managed to keep it mainly at 22 c. The other 2 were bubbling away pretty vigorously within 8 hours (temps with those were 25 to 28 c).
SG completely unchanged on Monday night.
It was still doing literally NOTHING by Tue night - 48 hours since yeast first pitched - no krausen, no condensation, surface of wort completely flat and undisturbed. I confess I didn't take an SG reading then and was just freaking out and threw the kit yeast in
Today the SG is around 1040 - definate change. Still no condensation, but krausen is appearing. There was evidence of pressure building inside: the airlock water levels were different, but not actively bubbling. I lifted the fermenter out of the bath to take a sample for the reading and the agitation had an instant effect - now bubbling regularly!
I agree it would seem unlikely to get 2 dud yeast sachets - but it seems plausible to me that if the issue was bad storage somewhere in the chain, it could affect a whole batch in the HB shop.
Other factors I can think of that may have had an effect: I didn't aerate the wort enough when pouring into the fermenter, and also, to keep the temps down as much as possible, I put 2 bottles of frozen water (thoroughly cleaned and sanitised on the outside) straight into the wort in the fermenter (seems unlikely to me that this could have made any difference).
Now that I have bubbling, my main concern is that I may have acquired some infection during the inactive period. The wort smells extremely sweet, almost but not quite sickly sweet - not really hoppy like it did at first. I drank the sample I took today
it didn't taste infected (not sure exactly what I'm looking for though).