Ahhh -- the olde fashioned meade recipe; formulated by beer brewers about 25 years ago because they had nothing else to base a recipe on! Well, based on this, there may be some things other than cooked yeast to blame for your failure to start a vigorous fermentation. First, mead musts are inherently low pH (rather acidic), so the addition of acid blend, orange juice, or any other acidic adjunct will likely stress out the yeast and will usually significantly slow fermentation. You ideally want a must pH in between 3.5 and 4.0, as this is acidic enough to prevent many spoilage organisms from taking a foothold, but still in the range where yeast thrive. Lower than about 3.4, yeast start to get stressed. Lower than 3.2, and many strains of yeast will fail to start fermenting. This especially could be your problem if you mixed up your must with water that is on the acid side fof neutral to begin with. If you can afford one, get a pH meter and check the pH of your must. If you can't afford the meter yet, then I'd suggest taking about 5 grams of potassium carbonate or potassium bicarbonate and dissolving that in a little water, then pitching that into your must. It will act as a buffer, and slightly raise the pH, counteracting any negative influence of the acid blend. BTW - acid blend does have some use in mead, but it is best added only after fermentation has completed, to adjust the flavor of the end product. Following close behind acid blend as something not to use in mead must is irish moss. It is a fining agent, principally used in beer brewing to latch onto plant proteins and to drag them out of suspension, reducing the amount of haze left in finished beer. Since you are not fermenting a grain beverage, you don't have any of these plant proteins to worry about and you don't need irish moss added at the boil. Third on my list of things you don't need to do for mead, is the addition of gypsum. Its principle function is to -- oh, oh -- acidify beer wort, to again provide a good pH range for yeast while shutting down spoilage organisms. But this is mead must, and we're acid enough already. Again, the dose of potassium carbonate ought to cure the problem of a too low pH, so you really should get some and try it, even if you can't measure the pH of your current brew.
So, there are the things I'd check and do first, before even pitching a new pack of yeast. Don't worry too much about the fact that you boiled your nutrients -- they lost potency in the process but you can always add a little more. If the pH balance fixes your problem, you'll see fermentation start within 24-48 hrs of the addition. If not, then I'd pitch a new pack of rehydrated yeast, and I'm sure you'll see some activity soon!