The Azdgari Warship is never available. If you want it, disable and board. Don't worry, the disable/board penalty is at worst about 10, so with a good enough reputation in Azdgari space no-one will mind (and hijacking one of their warships up in the North Tip area is too far away for the Azdgari to notice, I believe)
Azdgari missions are notoriously difficult to continue. Just go everywhere about five times, and you'll get the next in the line. Personally, I never completed the Azdgari mission string - the ethics of working for my least favourite Strand finally got to me, and it this point, it DOES become hard to continue. Just look around. I'm not certain where exactly to go, but it's always more fun if you're not positive. Work at it!
I'm pretty sure it ends with a major objective of Override completion sign, so don't give up until then (and not even then if you're using plug-ins).
That UE string is available about the same time the Paaren Station missions are available (right after signing up). Try Earth, and perhaps major planets like Paaren. It's there, you are probably just unlucky enough to hover around the % chance of no mission all the time. It's "Rescue Scoutship Crew". Leads on to the dreadnought missions, BUT, after investiating the Isled System, the next mission has a low percentage of occuring. The idea is, you don't get to kill the dreadnought for a few months.
To get around low percentage chances, pick up a mission at the mission computer, and abort it. It'll reset the missions both in the mission computer, and the chance of getting an available mission in the bar. To note, don't do this in Miranu space. They get pissed off.
Esponer
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Word.