Mission 5, then 10, and now 20 are not available to me, and the only thing the Agent says is
"Sorry, kid, nothing at the moment. Could you come back later? "
Yes I know to contact support and so far they have helped, but itsfustrating that it keeps happening. I am expecting it to happen for another 3 or 4 times while doing the Arc.
It is usually because somebody else is in space with you accepting the mission at the same time. If you try again a few seconds later, it usually goes through.
The mission should be in your journal, along with the agent that is offering the mission. You can also find the current mission by opening up the missions tab, going to the epic arc, and looking at the last mission. At least, I think that will work.