A 2-0 defeat in Belgrade against Red Star on Tuesday made it three successive away Champions League losses and put their qualification from Group C in the balance.
PSG's 1-1 draw against Napoli keeps Liverpool top of the table on six points but only on goal difference from the Serie A side with the French champions a point behind.
A daunting trip to the Parc de Princes awaits on November 28 - although a win would guarantee qualification - and Klopp hopes to have discovered a solution by then.
"I don't say it is already serious if you lose twice but we have to make sure it will not not happen again as the next game is an away game (against Paris Saint- Germain) before a very difficult home game against Napoli," he said.
"It is too early to say how it is. We have to make sure in Paris that we do better. We will talk about that but we can't change it."