The Reds suffered a shock 2-0 loss to Red Star Belgrade in Serbia on Tuesday night.
Despite improving defensively this season, Jurgen Klopp’s attackers have lacked the same potency that drove them to the Champions League final last season.
And fullback Robertson knows they must begin to fire again in the opposition half.
He told the club’s website: “I think it’s one of those periods we need to get through. Last season everyone was used to us scoring four or five goals.
“That can’t be possible every single game. At times we’ve dug out results, in the Premier League more so this season.
“Maybe it’s not been as good to look at but we’ve been effective at it. Maybe we are missing a bit of a spark in terms of not winning 4-0 or 5-0 in most games but if he [the manager] thinks that then we need to try to get it back.
“We need to come together as a team and try to give what the gaffer wants, try to get the spark and try to win games more comfortably.”