Additional problem may be JumpGates. If memory serves, Civilian ships require jumpgates to travel to other systems.
Is the target colony within the same system, or in another system?
If the latter, is there a jumpgate to the target system? If not, you'll find the civilian lines cannot enter it and thus cannot take on tasks to deliver cargo there. And if there isn't a gate leading back, the ship will be trapped within until a return gate exists.