Another newbie question re: rebuilding a La Pavoni Millennium. I've descaled w/ Cafiza, replaced all the seals, lubed it up and put it back together.
It heats up fine, the steam wand releases a ton of pressure, doesn't appear to be leaking anywhere. All good. However, when I lift up the lever and try to do any sort of pumps, no water, nor any pressure that I can discern, builds and passes through the shower screen. Something seems to be blocking the
water. I've checked the metal group tube, and it is clear, and the screen itself is clear. When looking into the group, is it supposed to look like this (pic attached) w/ that plastic cylinder as placed? Thanks.

You can see that the water inlet channel of your sleeve is oriented near the neck of the group. On mine, it is oriented opposite the neck of the group, and I think that's typical. (See Stefano's post here, for example.)

But I think there is some variability in these groups and as long as the sleeve is fully screwed in, your different orientation of the inlet should not make a difference in the water delivery. (In theory, I suppose if the sleeve were somehow screwed in way too far*, that would raise the inlet hole relative to the piston which might make for feeble or no water delivery.)

Make sure you have the o-ring on the sleeve properly placed. Make sure your plastic group neck insert and siphon tube are well sealed and you have no cracks in the tube. And make sure your piston is not partially unscrewed on the piston rod, because that is probably the most common cause of your symptom.

*edit addition: I don't think you can screw it in too far because the tabs at the top of the sleeve are up against the ceiling of the group when it's fully in.