I just got to the point of upgrading my capital to the Enigmatic Nexus, which was fine, however afterwards I lost the ability to build a bunch of buildings such as Class-4 Singularity, Dimensional Fabricator and even Military Academy and Planetary Shield Generator, because they require an Administrative Array capital building, which the Nexus apparently doesn't count as.

Additionally, I've also researched the Dark Matter Power Plant and Pico Forge, and they aren't on the list of buildings I can build whatsoever, only Dark Energy Pylon and Dark Matter Converter are available,

Edit: Iodizium buildings also can't be built because they lack an Administrative Array.

Edit 2: I guess I don't really need them when I can convert the Frame World's districts into ridiculous dark energy/matter versions lmao.