Why was Vermont not one of the original thirteen colonies?

Vermont claimed independence from the thirteen colonies during the Revolutionary War. Though opposed to this unilateral declaration, the other colonies were not in a position to do anything about it while they were busy fighting the British. Nonetheless, the Continental Congress was still able to refuse to recognize Vermont as a separate colony.
It would take another fourteen years before Vermont would finally enter the Union as a state. Such a long delay was largely down to territorial disputes with other states. The state of New York vehemently opposed Vermont's entry into the Union because it claimed that some of Vermont's lands rightly belonged to them. As New York was such a powerful player in national politics, the state was able to get the Continental Congress to refuse to even discuss the case for Vermont's entry as a member of the Union. It was only when Vermont agreed to pay New York the then substantial sum of $30,000 that it was finally able to begin the formal process of becoming the fourteenth state.