New A/C compressor not engaging

Vehicle: 1500 with rear A/C and auto climate (rotary knobs).

Hey All,
The rundown:
The truck had a faulty A/C compressor clutch. Unaware of prior A/C operation. Decided to replace with a new factory AC Delco/Denso A/C compressor, along with a new accumulator and o-ring gaskets.
System was vacuumed for an hour and held vacuum. Set up the tank to fill system with 3 lbs of Freon. The new A/C compressor will not engage even though the indicator “snowflake” is present on the climate control unit. I could only fill about 6 ounces of Freon as a result.
Checked wire connections on the new compressor. They are good. Swapped the A/C relay with a known working relay. I then jumped the pressure sensor on the accumulator. None turned on the compressor.
I resorted to jumping pins 30 and 87 on the A/C relay pinout. This will engage compressor. I continued to fill the system while the compressor was running. According to the scale it would not fill all 3 lbs, but close to 2.5lbs

Main concern: Why is the brand new compressor not engaging when prompted from the dash control unit?
Any tips or directions where to go from here would be greatly appreciated.