Ambassador 3: Changing Fate. Ambassador: Science Fiction Thriller Series, #3

Fifty thousand years ago, a meteorite hit the planet Asto, giving its Aghyrian inhabitants mere days of notice. Three ships escaped the Armageddon. Two went to the neighbouring planet. The third, a massive generation ship, refused to take on refugees, and then vanished without a trace. It's coming back. Its initial burst of communication caused the outage of the Exchange, the FTL network for transport and communication, but since then the ship has been silent.
It jumps about at random, using wormholes it generates with a drive the likes of which no one has seen before. Meanwhile at the gamra assembly, people jostle to be in the best positions when it inevitably turns up in inhabited space. What the ship wants or whether there is anyone on board no one knows, but diplomat Cory Wilson knows one thing: when it turns up, he must avoid a conflict at all cost.
If only gamra presented a united viewpoint. If only Asto's army wasn't keen to get involved. If only the Aghyrians at gamra didn't do what they do best: manipulate and play games with everyone. While the ship approaches, the delegates bicker, and the time for negotiating is fast running out.