Check again for the seal from the old filter. I replaced my filter recently and put everything back together but failed to remove the old seal. When I installed the new filter I thought to myself that it wasn't going in very far. Only when I looked online to find out what the yellow plug was for did I see to make sure that the old seal comes out....checked the old filter in the trashcan and it wasn't on the neck.
Had to drop the pan again to pry out the old seal. Then the new filter would seat better. As soon as I put the new filter in, I closed up the pan to hold the filter.