Have you built a War Planner's Desk, yet? You could try to schedule a raid via the desk and see if that works. Sometimes, it works when Jammz is jammed.
@uituit is faster and more concise than me.
Also, check the settlement report on the war planner's desk. It will tell you the breakdown of all your recruits' various roles. You need at least 5 Warriors to launch an attack. If you have auto role change set to "on" in the conqueror part of the City Planner Holotape, it's possible, depending on the situation at abernathy when you took it over, that auto role change switched some "warriors" to "guards" (guard posts/martial plots) and/or "workers"(Commercial/Industrial/ Ag Plots). If it switched too many, you won't be able to launch an assault until you change enough back over to "warriors."
If you have Soldier's Needs "on", then regardless of how many chems or caps you donate, you won't be able to recruit any new troops until all your Wages/Rations/Equipment needs are met.