hi, welcome to the forum!
that's a somewhat "known" bug, we don't know why it happens.
so it would be really great to have an earlier save, before you completed the latest stage of the sickle questline.
(we'd need the *.skse file too, the forum doesn't like the format, please pack them to a rar or zip or something)
thank you
- [+] to the workaround
-
- open the console
- type player.moveto 13b6fe and press ENTER
(- close the console?)
- you should now stand directly next to the courier (in Ark); talk to him and the quest should continue
hope that helps
