My wife and I were trying to sort out this question. We know the Jews are God’s chosen people. It does not escape us however that they continue to reject Jesus as Messiah. To summarize our conversation: one of us said not all Jews will be in Heaven because not all will accept Jesus as Messiah. The other said, Jesus is coming back and all Jews will accept Him as Messiah because the Jews are God’s Chosen people and He will save His chosen people.
In John 14:6 Jesus said no one can come to the Father except through Him. He made similar claims throughout the Gospels. I believe the majority of Jews who are alive just before the 2nd coming will accept Him as their Messiah and go into the Millennial Kingdom (Zechariah 12:10). But all of the Jews who lived and died between the 1st and 2nd comings without doing so have been irretrievably lost just like every body else who failed to accept Him.