Why does my mazda tribute only start intermittently?Details below

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I've used one new key for about 5 years then I started having problems with it starting only when it wants to.So I used second key then worked fine until 8 months ago it did the same thing as first key.only starts when it felt like it and when it did crank over it ran beautiful!No dieing out nothing just when I stop it then took forever to start.The last 3 weeks has become harder to start.So I had a locksmith look at my key lock and it's all good.Then I bought a ignition switch from dealer and a coil antenna sensor changed those out and the same problem.so I just put the original two parts back in.I had the starter tested with a meter for voltage and no voltage so I had starter removed and took it to be tested it tested good.No current or voltage seems to be reaching starter from main things like switch, starter relay etc to crank it.I also checked relay only by testing fuse box which is fine took out relay and put back in there is no way of testing the starter relay unless I ordered a new one which I didn't do.I checked all fuses related to starting all are fine.My pats security theft light is working like it should there is no fast flashing which will indicate a key trqnsponder issue.My key seems to work fine and unlocks/locks good.All my dash lights work like it should and no check engine lights come on.I've never seen a vehicle do this ever.when I try to start it I can only hear the fuel kick in like it should and a little clicking sound from the black fuse box where relay.My battery/altinter are both good.What else could be the problem? Could it be crank shaft, Trans sensor etc? Thanks for reading this.I know it's long and Thanks for any help you can provide!