A mod conflict, likely with Gigastructural Engineering, makes it impossible to find the Reesan key: the special project "MEM_FOOD_CONSTRUCTOR_RECLUSE" does not show up, and no segments are habitable. All events up to and including "mem_food_constructor.12" (Reesan Operations dialogue) work as designed.
My hypothesis is that some conflict with Gigastructural Engineering makes the system not generate properly.
Below, images of the completed previous special projects and images of the bugged system:

All ring sections are uninhabitable, as shown above with "Shipping and Receiving".