Stuck in the mission with the spirit gate and I can not warp jump with spires flag ship!

I played the mission where you need to take the spirit gate artifact by sending troops on to the enemy vessel. But after doing so the enemy ship resets and no matter how many times you try this method it will just keep on reseting. Now I went to the Battlefleet Gothic Armada discord with my problem and they told me that I needed to warp jump to proceed with the mission, but for some reason this option is not available for any of my imperial vessels, the button greyed out.
I am stuck and it is impossible to proceed. I have tried restarting the mission, skipping turns and so on, but the problem still remains, when I am supposed to warp jump out of the fight, I can't do that. Once I waited for a good 10 mins to make sure that it wasn't just a time thing or that I have to wait for the dialogue to play out, but the option to warp jump remains unavailable, even with just spires flagship selected.
alt text

I'm still having this issue today as well.

So I've beaten it again now, this time my issue was that Spire's ship had a debuff BEFORE the battle that prevented it from disengaging. I had a spare ship in his fleet, promoted him to that, and was able to beat it.