PPS sticking in the barrel

I am trying to injection mold non-filled PPS.
My barrel is about 1meter long and my temperatures are
295C nozzle
297C barrel #2 near the nozzle
296C barrel #3
262C barrel #4 nearest the hopper

I have about a 6 liter hopper and a drier near by. The goal is to transfer scoops from drier to hopper as needed to keep the hopper level about 10 inches above the screw.
I have the back pressure near zero less the friction of the slide.
My shot travel is about 100 mm out of 250mm of total travel.
The motor will not turn the barrel. When I vacuumed the resin from the hopper throat, I can see compacted resin on the screw. I am on the low side of the temperatures per the resin directions.
Any suggestions?

I have never run that before, but just glanced in my book and the temps appear to be well below the lows in my book. Might look up the temps again and raise them. Low in my Ashland book is rear at 560 F to 580 F at the front. Highs are 600 F rear and 620 F at the front. Guess I could have converted those to C (sorry on the end of a 14 hour day). It is a semi crystalline material so probably isn't melting as it has a narrow temperature range for processing

Why is the back pressure near zero? Back pressure is what creates the resistance that makes the screw do the work that generates the shear heat that melts the resin ...