The science pack is recipe requires a surface pressure (HPA) of 5000. Nauvis and Nauvis Subterrain have a pressure of 1000. The only plant that I could make science on is anothe rmodded planet Parcellscis, which is obviously unintended. Screenshots on the main page show assemblers underground making science so I don't know what's going on with this requirement, but I can not advance on this mod.

You are correct, that is not intended. The surface pressure and science pack required pressure are set to the same value. What other mods do you have enabled? I wonder if one of those is re-setting one of the pressures

You are correct, that is not intended. The surface pressure and science pack required pressure are set to the same value. What other mods do you have enabled? I wonder if one of those is re-setting one of the pressures

Metal and Stars
Paracelsin
Planetaris:Arig
Planetaris: Hyarion
Planetaris: Tellus
Secretas&Frozeta
Vesta
Alien Biomes Graphics
Armored Biters (Specifically 1.2.1)
Castra
DataCpt Utils
Diurnal Dynamics
Enhanced Shadows
Fall of Promethea
Kyyzeth Standard Library
Moshine
Subterranio (Base, Nauvis, Fulgora, Vulcanus)

That's everything that might affect planets statistics (excluding mods like nixie tubes, inlade lamps, eta.). As a note Subterranio was installed late into the playthroughs cycle (finished Vulcanus, Fulgora, Gleba).

I made a branch save in which I unloaded the mod, then reloaded the mod and did the steps necisarry to unlock the tech. The cave layout remained identical and the 1000 hPa issue remains

Heya!
Found the error source - there are two constants.lua files, in scripts\ and prototypes\surfaces\ and only one of them is loaded in that specific script.
Thanks for the mod btw, playing it with islands world, just actually got to underground.

Thanks for digging into it more! Is it fixed now? If so, what was the change to make things work?

Thanks for digging into it more! Is it fixed now? If so, what was the change to make things work?

Yeah, I didn't try to rewrite the mod, just fixed specific script with a quick edit.
subterranio-nauvis_0.1.8\prototypes\surfaces\subterranean-surface.lua
just change constants to actual numbers
pressure = 5000,
gravity = 20,

Don't need a new game, just load and underground will now have correct pressure to craft the science pack.

This should be fixed (for all the underground areas) in 0.1.9 now!