I am having the same issue.
From My experience and knowledge of DC Electrical systems I believe it could be…
The ground wire (negative). The connection between the ground or (-)/the black terminal/negative lead (post)on the battery and the end of the wire where it connects to the lower part of the engine on the right side.
OR
The Neutral Safety Switch.
OR
The ignition (we here you put the key) is bad.
OR
The stock anti-starting portion of the stock security system. Or a add on Security system.
OR
A bad fuse
OR
The Starter Relay needs to be checked. Because it might be in need of replacement.
OR
A connection somewhere on the Starter or between the Battery and the Starter.
Check to make sure It is all the way in Park (P) or Neutral (N).
Check the fuses, Starter Rpelay and connections and the ground wire.