Aj's 818S in Houston

[Bob_n_Cincy]

So, it cranks but does not fire?

As for the fans, I too experienced this to some degree. At times they do not come on at start up and other times they come on instantly. I really have no explanation for that. Perhaps it remembers some state from shutdown or something. Also, if the battery went stone dead as you say the ECU lost its brain and is starting off fresh so, all bets might be off until it runs a bit and relearns things.

A CEL (Check Engine Light) will often trigger the fans to come on and stay on at start up.
If your battery was disconnected or dead, the ECU must relearn the cam and crank sensor relationship. It usually takes an extra revolution to start.
I turn off my battery every night, so this is normal for me.
Any chance you plugged in the green connector?
Do you have multible wires connected to the battery? Maybe you misses one.
Bob