Without examining your return (we can't see it in this
forum), it's impossible to say exactly what caused your refund to decrease or taxes owed to increase.
However, there's a high probability that at least one reason is listed in the
FAQ below. I recommend printing your 2015 and 2016 returns and comparing them
line by line to see what changed.
https://ttlc.intuit.com/replies/3301788
