like glenn said above, give the plugs a wiggle. that was my issue too, slapped a ziptie on it and its good to go!

There will be no power at the compressor plugs for 2 reasons.

The low or high pressure safety switch is not letting it get power

or

There is no power to the safety switch. That's it really for common stuff. Unless you just wrecked it then the problem should be one of those.

I second not messing with it if you don't know much about them. It's real easy to screw something up. I doubt you have a vacuum pump to evacuate that new gauge set and believe it or not just hooking them up will let enough air in the system to screw with a 134 system. Seriously. It's an electrical problem it sounds like and you should really just stick to that side of it. Jump the low pressure switch with the truck running and the ac on max with the fan on high. It's the one on the receiver dryer. It's in the back right side of the engine compartment on the heater core box. Round metal cylinder looking thing with a sensor on the side of it. That is the low pressure switch. Pull the connector off and jumper the connector.
It was already said that the connector is notorious for bad connection. It's true. Same thing with the master cylinder level sensor. The female wire ends in it get corroded and it loses it's connection. Then the ac doesn't work unless you wiggle it. Sometimes. It's usually cleanable or fixable. With the ac set like I said if it comes on when you jumper it and the lines are cold and the clutch is staying engaged then the charge is probably ok. Assuming someone that knew what they were doing charged it. Most mechanics don't anymore so don't get your hopes up. It's not their fault really. They just do what those stupid computer recovery machines tell them to do.

Update
 

Here's an update on what has been done so far
Took everyones advise and took my truck a guy that has all the proper gauges and knows about A/C. Keep in mind I had already purchased a couple of cans of freon.
He hooked up the gauges, showed to be empty. Put one can in fine, jumped the low pressure switch and the compressor worked. Plugged the low pressure switch back in. Compressor started short cycling, still low. Then all of a sudden, his low side gauge pegged, just like mine did. He said for some reason, the low side is being pressurized, he had never seen this happen. Since low side has more pressure than the freon cans, it won't take any freon. We didn't try to add it after we foun out it had pressure. Not being able to add was our first indication.
So, here is my question. What would cause the low side to have that much pressure?

Orifice tube might be plugged. I'd pull it and check.

I was just told to try that first. Got the tube, but having trouble locating the tool.

Thanks a million to everyone that offered guidance and didn't make me feel like an idiot.

Update
 

Here is an update on what is going on so far. I took everyones advise and had a guy that has that gauges and has worked on many A/C systems. We jumped the low pressure switch and the compressor worked. Hooked up the gauges and it said it was low on freon. Pulled a vacuum on the system and attempted to recharge it. We started using the small cans rather than the large 30# (because that is what I had purchased already). First can went in fine. Stopped to switch cans, second can would not go in. Checked gauges. Low side gauge was pegged

With the compressor off the low and high side will equalize and you would see high pressure but not when it is running.

Sounds like you have debris in your system and either the orifice is plugged and/or the reed valve in the compressor has some debris in it keeping it open. You can buy the tool really cheap to open up the lines and IIRC all you need is a long set of needle nose pliers to remove the orifice filter. Your compressor maybe going out, check the orifice filter if it's got a bunch of **** in it. If it does look further into it before dumping in more freon.

Here is my update so far. Replaced the orifice tube. Pulled a vacuum, but not where the A/C guys said it should be, could only get it to -20. Recharged the system. Found a leak at the high side service port. Bought the repair kit, but the Schroeder valves were the wrong ones. A/C is working now. I figure that when it leaks down again, I will get a new port for the high side. Thanks a lot for all of the guidance.