Liverpool thought they had opened the scoring in the Carabao Cup final when Joel Matip headed home in the 67th minute.
Trent Alexander-Arnold delivered a free-kick to the back post where Sadio Mane nodded the ball back across goal for the Reds defender to finish.
However, it was ruled that Virgil van Dijk - who was blocking Chelsea's Reece James - was offside in the build up and the goal was chalked off following a VAR check.
The red half of Wembley roared as Matip appeared to break the deadlock, but celebrations were short-lived.