Hi. Sorry for the troubles. I've replaced my resister several times, and finally the pigtail. Then cut off the pigtail and hardwired after it failed too. It seems that arcing between the resistor and it's plug are most often the problem. Anyway, here's what I would do.
-Find a good chassis ground for your volt meter for testing. Check the plug on the blower motor again. With the ignition "ON", you should see 12 volts on one side of the plug (dark green wire). If still no voltage, then you have a wiring issue between the ignition and the blower motor plug (wiring, fuses, ignition switch, etc, etc). If you do get 12 volts, then go to the next step.
-Next check the other side of the plug (dark blue with yellow wire). This wire will go through the resistor pack and the fan speed switch, to ground. Set your meter for resistance (ohms). With the fan switch on "high", you should see good continuity to your chassis ground (low number, preferably zero). On the medium and low speeds, you should still have continuity to ground, but with increasing resistance. "Off" should not have any continuity to ground. If you don't get continuity as described then try the next step.
-Next pull the plug from the resistor pack. Here you're checking for burn marks or other evidence of arcing between the resistor pack and the plug. If you see it, that may well be your problem. My new pigtail didn't last long before it arced and quit working. The burn marks were obvious. If no burns, next check for continuity on the dark blue/yellow wire, front the blower motor plug to the resistor pack plug. Continuity should be good, it's just a length of wire. Then check the remaining wires on the resistor pack plug, for continuity to ground. You'll have to change the fan speed switch to check each one. Black/tan for high. Light blue for medium 2. Light green/yellow for medium 1. Tan for low. If these check out, then your fan speed switch and ground connection are good.
-If good so far, you can hotwire around the resister pack to check the motor: plug your blower motor back in. At the resistor pack plug, jumper the dark blue/yellow wire to the black/tan wire (a length of wire or a paper clip will do). With the ignition on and the fan speed switch on high, the blower motor should run. If not you'll have to go back and do some re testing.
-If everything checks out so far, that just leaves the resistor pack. Sometimes new ones are bad too. I understand you should see continuity across any of the connections, but I check from the one that plugs into the dark blue/yellow wire, to each one. You should see continuity with varying resistance. If no continuity, replace the resistor pack again.
I hope this helps. I know you've gone through a lot of this already, but I wanted to leave a tutorial that others could go through as well. Non functioning blowers seem to be a recurring topic, and I wanted to share what I've learned. Disclaimer: use at your own risk, and wiring is likely different on 99 and earlier trucks.
Good luck and let us know how it turns out.