Comey did not say that "the Russians did not have any affect on any vote in the last election."
Here's the actual exchange:

BURR: Are you confident that no votes cast in the 2016 presidential election were altered?

COMEY: I'm confident. When I left as director I had seen no indication of that whatsoever.

"affected" and "altered" do not have the same meaning. Burr was asking about hacking of the electoral process itself, not about hacking of news sources, planting of fake news, and the use of bots to rapidly disperse fake news that was gobbled up by some right and alt-right media. Burr was not asking about whether the Russian disinformation campaign affected how people voted; his prepared question, which he read carefully, was about whether votes were altered after they were cast — and that's the question that Comey answered.