Some scholars have disagreed on the meaning of this prophecy in Isaiah—specifically how to interpret the condition of the woman who would conceive the Messiah. The original word in Greek describing the woman is parthenon. This is normally interpreted as "a virgin" but can also mean "a young girl." In the ancient world, women married at a young age and would be young when they conceived. Christians, of course, view this as a prophecy about the virgin birth of Christ. In the Greek world, the word parthenon clearly indicated virginity. However, that was not necessarily the interpretation in Hebrew.
It is important to understand that Isaiah was prophesying that there was going to be something really unusual about this birth. If it were just a girl getting pregnant, that would not be very extraordinary—there would not be much to this prophecy. However, Isaiah’s prophecy indicated that this was going to be a special birth in some way. It was similar to other prophecies of unusual births in ancient scripture—like saying that an octogenarian woman was going to conceive (like Sarah, wife of Abraham or Elizabeth, wife of Zacharias). Isaiah was stating that there would be a very unusual birth and this child would become the Mighty Counselor and the Prince of Peace.
Even though a large number of Jews rejected the Savior, we should not forget that there were many Jews who did accept Jesus. In the early days of Christianity, Jews were the main group of people who converted. Matthew was one of them. Matthew saw Jesus as the fulfillment of prophecy. Paul, also, was a Jew. Where did Paul teach? His first stop was always to the synagogue in every town where he preached. These were the people who knew the prophets. They were the ones who knew the tradition and prophecies of the Messiah. They could see how Jesus fulfilled all of these prophecies. Therefore, there were many Jews who did accept Jesus as the Messiah. We can be very grateful for that.
Book of Mormon Central, "How Did Nephi Read Isaiah as a Witness of Christ’s Coming? (2 Nephi 17:14)," KnoWhy 40 (February 24, 2016).