I have a 96 gmc 5.7 vortec I parked my truck for a couple weeks now it won't start I've tried starting fluid changed sparkplug made sure I was getting spark but it just won't fire

So it did not fire off with the starting fluid? And so do you have spark?

I have spark and no it wouldn't fire at all

I cleaned mass air flow I changed sparkplugs I don't no what else to do or what it could be

I am thinking fuel pressure. It should be 56 to 63 lbs at the schrader valve on the intake manifold.

But it should have fired off with the starting fluid.

That's why I'm at a complete loss as to what to do now

Is there a security system on there? If it is on it shuts down the power to the injectors. Try shutting the security system off.

No it has no security that I know of that I can see or find

Well you would think it would fire off with the starting fluid. An engine needs fuel, spark, and compression to fire. Maybe do a compression test?

The only other thing I can think of is to disconnect the battery for at least 30 seconds. This would re-set the computer, then give her a go.

So I tried all this and I'm still not getting nothing

Alright then, I don't see where you have addressed the fuel pressure. Need to verify if you have 56 to 63 lbs. Next or what ever order you want to go, Need to check to see if there is voltage at the injectors. And then a compression test would need to be done. You say there is spark, well thats a plus.