Truck not starting

[workking1]

Truck not starting after switching batteries
1999 Gmc Sierra Crew Cab
This truck is a transitional year, i have the replaced version, 454 vortec fuel injected engine.
I replaced the 2 batteries in january of 2015, i was having an intermitant voltage reading on the dash board gauge, where it was charging at 14 volts, then out of nowhere it dropped to in the red at 9, then it would come back later. I switched the two batteries over yesterday, disconnecting the negative first, then the positive, i then connected the negative and then the positive, i went to crank over and got nothing, no clicks, nothing, can you explain, bad alternator, short somewhere, did i connect them in the wrong order, one battery is main, the other is for the power point which i never use.