An engine needs three things to start (and run): air, spark, and fuel.
I'm assuming that it has enough air to start -- your intake system and filter would have to be completely plugged for this to be an issue, and it's likely not.
I'm also assuming that it has enough spark to start. Sure, one coil may be flaky, but with the other five coils, it would start and run, though it'd certainly be a little rough. I hate to ask you to check the obvious, but since your husband replaced the spark plugs -- check to be sure that the spark plugs are torqued correctly and that the coils are fully seated on the plugs, are retained by the small nut or bolt for each one, and are plugged in with their harness connectors. In the excitement of changing them out and trying to get it to start, I suppose it's possible that the wiring connections to the coils were forgotten (so none of them would be providing any spark).
If it cranks smoothly and doesn't even cough or attempt to start, then I'm guessing that it's not getting fuel. I would check the fuel pump fuse closely; swap it with a similar fuse even. Turn the key on (but don't crank it) and listen for the fuel pump to run for a few seconds. If you don't hear ANYTHING when you turn the key on, it's likely that your pump is not running (for some reason). It could just be the fuse.