I have a plunger tub drain. We have never been able to engage the drain because the lever is locked in the down (open) position. I purchased a new overflow/lever housing because I thought the spring may have been bad. I just went to install it and the lever still won't go up! Could there be a blockage at the base? It doesn't feel like the plunger is going down all the way, so I don't know if adjusting the arm length is worth wile.