Bought Trailblazer was running on two cylinders ran out of gas, put gas in try to start it backfired now just cranks no start

What is your question?

Replaced camshaft actuator valve, put gas in it it tried to start backfired, I have no spark now, won't run, crank sensor good, camshaft sensor good it's getting gas just no spark all fuses checked none blowed

How long has your 2003 Chevrolet Trailblazer had this problem?

Been setting for 3 months now