Bad luck with yeast?

Hey everyone! Just getting back into brewing after a long absence from the hobby. I brewed up a brown ale on Sunday and I'm waiting on it to ferment, but the yeast isn't doing anything. It was old yeast (to the tune of around nine months), so I waited three days before calling it lost and buying a new packet. Added that last night, and I noticed a lack of any krausen at all when I opened up the pail. Cut to 24 hours later and I'm still not seeing any activity in my airlock! Does anyone have ideas as to what's going on?

Some more info: Fermentis US-05 yeast in both cases, rehydrated at ~80F (foamed up both times), sitting at around 65-68F ambient. The first packet came with the kit, and the second I bought out of the fridge at my local homebrew shop.

Some of the liquid from my airlock got sucked into the pail due to a temperature drop, but there's no way that a portion of a normal 3-piece airlock's worth of water with a little one-step in it would be able to kill my entire batch of yeast twice, is there?

The airlock wouldn't have had any effect. The first yeast likely was bad. Given that it's been almost a week, I see two issues. The first is actually it's only been 24 hours and could take up to 72 to get going, even if it hasn't done that before. The second probably larger problem, did you re-aerate in any fashion? If all of the oxygen came out of solution in the wort, the yeast can't get going. May need to stir it up a little bit or shake it around to get a little O2 in there. I would also check your gravity just to see if it's moved at all. Were you in the 1.04 range for your OG? Bigger beers can take longer to get going and also you could have underpitched.

Just wait. you be aight.

Thanks for the advice, everybody! I had found a Fermentis pdf saying 78-87F for rehydration, but that was a general guide. I used the temp from Palmer's book the first time (~95 I think), and I was nervous about killing them with heat when I repitched. Aeration seems like a good plan; I hadn't thought to stir it back up when I added the second packet, so a good shake couldn't hurt anything. Waiting is also probably good advice, but it would really be more like "sitting around worrying about my beer."

Hopefully some air and time will wake the dumb yeasts back up, and I can get back to entertaining myself watching my roommate's cats freak out about the airlock's clicking noise.

Had dozens of successes with US05 and never rehydrated once. Just sprinkle it into your aerated wort (I shake the fermenter like crazy before pitching), just like it says on the packet. Gets started within 12 hours normally.

I gave the fermenter a good shake about three hours ago, and the bubbler's ticking nice and steadily now. Looks like all the new yeast needed was a little oxygen! I still think the old stuff was stale though.