Yes, he lied about what he knew. Which is in reality nothing.Mueller stated in court that Manafort's lies pertained to 'the heart' of the Russian electoral meddling case.
If he knew something they would cut a deal. This kills all chance of his testimony.
I'm betting it involves his transfer of polling data. It's quite probable he took money for it. The question is did he do it before it after he was fired.