As always look for something simple. I went through a slew of intermittent no start conditions including tows. The problem
I believe was the VATS system. If you try to start it ,but Vats detects an error, you'll get power but no starter and no fuel pump.
Could be a misread of your key resistor, could be the transmission switch. All you can do is organize a check list and go through it one at a time. There is a ton of info on the internet. I got so fed up with mine that the final cure was to install a VATS by pass from New Rockies. Wasn't cheap and it bypasses the entire security system, but ...it starts.