How did you bleed the assembly to ensure there wasn’t any air inside? I would think in that type of setup you’d almost have to assemble it submerged in a tub of fluid, or at least have it full to the point where you’re squeezing it out as you assembled the pieces. I used to rebuild the Fox shocks on my brother’s Tacoma and my Swayaway 2.5 on the Bronco regularly. Both has their own procedure to remove all the air.
There is a bleeder screw at the bottom of the reservoir. One thing I didn't mention above, but RPG covers in their video, is the bleeding of the nitrogen and install of the schrader valve.
The shock retains all the fluid as long as you leave it with the solenoid valve facing up.