My Kindle won't turn on. What's the problem?

A friend of mine gave me his old broken Kindle Fire and said if I can fix it I could have it. I thought the problem was in the charging port because before it completely broke it would only charge when the charging cable was held at the right angle.I replaced the charging port and charged it overnight, but it still won't turn on. I have tried the resetting option but it doesn't do anything.