It is a shame that the early model Trailblazer and Envoys did not sport a Fuel Pressure Schrader Valve Port, right off of the Fuel Rail where it could be more easily accessed for Testing Fuel Pressure… and while we’re on that subject,
@budwich mentioned earlier about the "curious dryness" of the Spark Plugs… so perhaps the Fuel Pressure Regulator has gone sideways and is not allowing the fuel to pass through the fuel rail.
I think
@Locksmith might have "The Key" to answering this problem ...because in these GM Ignition Designs... The PASSLOCK mechanism is nested within The TUMBLER and if IT has gone T*TS UP... Replacing the Key and Tumbler as a Set from a GM Dealership might just solve this problem. This Video is for Demonstration purposes only of How the Key Tumbler works... You won't have to go through the use of an Air Tool to get yours R&Rd:
And beyond the PASSLOCK problem if doing that repair does not get the SUV running again... it may wind being a Bad PCM. While this video shows the value of having a Tech2 and a Lighted Probe to Diagnose a
No Crank- No Start condition… and even though this problem is not
exactly like yours… The VOP (Video Original Poster) proved that the replacement Swap-In PCM was “ScrabNoid” in midstream during updating because of the
sketchy wire signaling at the Ignition Switch involving the Pink Wire. So the original PCM needed to be put back in as “VIN”ed to that TB... and it would be necessary to Replace The Ignition Switch FIRST prior to re-programming the PCM to operate properly again. Unfortunately, this is the kind of Diagnosis that does NOT lend itself to 'Pure Mechanical Intuition' in order to get fixed and few other Scanners can perform such repairs such as this one: