I just saw this. I do not have a good answer for your question. I hope you do not have to go back to an earlier point. Give me a little bit of time and I will look into it - about a day or so.

Okay. I looked at it. Here is what I did:

I went to the Mechans and talked to them and gave them wrong answers until they were hostile and armed their weapons and started shooting at me. When I encountered them at the guarded planet, Heaven, they told me, "Respond, Intruder" and "Turn away, Intruder or you will be destroyed."

This appears to be because they are guarding their "Home Planet" and you are currently hostile to them. Here is what you need to do:

Encounter the Mechans, but not at their Home Planet. It can be in their Home System. That is fine. They will hail you and tell you to respond. Keep answering their questions correctly. If you really blew it, then they will just ask a few questions, then terminate communications. Keep finding them. Be patient. Eventually they will lower their shields and tell you, "Our data banks are at your disposal."

The planet, Heaven will no longer be guarded.

Does this work for you?

Without hitting you with a bunch of spoilers, the Mechans' questions are related to one of the Old Empire's final Noah colony missions from the 3470s. I could tell you the proper answers, but then you'd miss out on discovering what it was all about! :) Actually, there are a bunch of web pages that will walk you through this part of it if you really want to Google it.