If my wife filed for divorce in 2012 and I did not respond, is it still active?

Most likely, a Default was taken and a Judgment was entered. Check into it and get a copy of the Judgment, it spells our your rights, assets and debts awarded to you, and responsibilities. If no Judgment was ever entered by the court, you may still respond and have your voice heard when the court is deciding child custody, visitation, child support, spousal support, division of assets, and responsibility/division of debts.