This has been bugged since release. About a gazillion complaints about it not completing, especially when teamed (ie. for accolades). So far Cryptic hasn't even responded to any of the threads that i've seen.
I never had the problem with main, who had rank 2 diplo when he did it. However my alts have this problem, due from what I could tell, them being unable to get Shon and S'Tasz to sign on. Without high enough diplo the only choice sellectable on each of those two equals disaster. Therefore mission utterly fails. Do over!
I have had the exact same problem multiple times, I submitted a ticket in-game. However when I went to look on it's status it wasn't there. This mission bug is really annoying and they still haven't done anything about it.
Close the warp window, open your journal and hail Achebe to complete the mission. Only warp out after collecting your rewards.
Completed the mission, convinced all the diplomats, got the Smooth Talker acolade, than saved all four ships, got the Champion Chaperone acolade, than Warp to Bajor windows popped up, which I minimized (there is really no other option here just Warp to Bajor, there is no Not now button as usual. So most people just warp. But I did not. Still the mission does not complete, the In Progress tab shows as a mission in progress, but having the starting description. Hail Starfleet button is greyed out, and there is no other way to contact Achebe.
Basicly, the mission either finishes, or it does not, and there is nothing you can really do about it. As shown, even if you do everything by the book, you can still have it go wrong.
(Character has T4 Diplomacy, too)
Wanted the Jem'Hadar pistol by the way, and of course I did not get it. Perhaps the mission completion routine could lack the chance factor, I see how it works for lockboxes, but missions should not behave this way, I think.
ive tried droping the mission, collecting before warping out, loging out and back in, and still it won;t let me complete it on an alt toon, its getting annoying playing the same mission to achive nothing.