Also, one thing to note, is the FC owner's behavior, esp if they are colonizing a system. Alot of FC Owners are using their carriers as staging areas to drop off goods, and setting cheap buy and sell orders because that is faster to drop stuff off, or load up their haulers than using the cargo transfer. And as a result, so they won't get robbed while they've ostensibly set their carrier sell orders to extremely cheap, they've locked down their carriers to friends only, or even solo.
the tl;dr is: they are using their carrier markets as shopping lists, and as such don't want to get robbed trying to do their builds.
Are the carriers you're trying to land at, either AT or near the primary star? Or at or near a construction project?