Have done the first 2 ancients missions and research. The research that mentions the probe being available for deployment is completed, I can see it in the completed research tab. However the probe is unavailable for manufacture. The subsequent missions for the ancient weapons are available but completing them doesn’t enable the probe’s availability either.
It isn’t my first ancients play-through and previously I have had the probe available after the mission.
Can’t remember the exact steps but I left the ancients until mid-game. I think I completed the ancients research with bonus research from an exploration event and that a couple of researches completed in one go.