Blazer no start after tune-up

https://www.2carpros.com/articles/car-cranks-but-wont-start

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor,distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing

If both fuel and spark is present-check the valve and ignition timing, this will lead you to problems
with compression and valves opening and closing at the wrong time/broken or jumped timing
belt/chain.

Is it still at the shop? Did they diag it for you? It ay be a bad cap or rotor if it lost speak. Fuel pressure needs to be verified as well.

Roy