First time, I installed the metal tag (thing that triggers the sensor) on the intake cam upside down. As I just rebuilt the engine, there were myriad things that could have been FUBAR'd. It took a while to figure that one out.
Second time, I had done a job on the ICV or something and removed the wire harness from the sensor. Again, did an insomplete re-assembly and was left scratching my head when it wouldn't start. Mind you, with previous experience, it took far les time to troubleshoot.
There, I feel beter having admitted my dumb-ass-ed-ness
Dave