These work just fine intra-system, but they don’t want to jump / they give the “unable to carry outstanding orders” interrupt.
I have a jump tender on the jumppoint, and they delivered a shipment of colonists just fine when I ordered them manually.
The colony has spare room for millions of population, the system is not flagged in any way (danger or military only), the colony itself is on standard settings (destination of colonists, not military restricted).
I think the reason is that you are using jump tender. You don’t have a jump drive on the ship itself and the Jump Point is not stabilized. The ship can’t jump on its own, and the game logic doesn’t take jump tenders into account, because you can move them at any time.
Try the tick box just above where the list of current orders are, that will treat the fleet like it has a jump drive. Cant remember the wording off top of my head sorry, it is above the cycle tick box I think.
As said by CopyOfSatan, have you tried to stabilise the jump points along the path to that colony?
In this way, you don’t need a jump tender in any case.