I started on Quadromire and wanted to launch a space platform, but only Gerkizia was up for selection.

Whats the seed that you used?

I used 1642243051.
My guess however is, that due to having to /cheat for getting batteries researched (https://mods.factorio.com/mod/solarsystemplusplus/discussion/67a7b7b2c31f700384891f9b), I un-researched all post-white-science researches, which include the Unknown key: "technology-name.planet-discovery-quadromire". After having researched that again, I was able to launch on Quadromire.
Interestingly Gerkizia is not even one of the planets in my solar system.