Sometimes a small amount of the Hop Oil may be caught in the Hopping Inlet. If there is a small amount of liquid just after you've added the Hopper to your Pinter, this is most likely Hop Oil residue. This can simply be wiped away and will not impact the taste of your Fresh Beer or Cider.
If you find your Hopper isn't going down at all, this could be due to the Pinter being slightly too full and there not being enough room for the Hop Oil to enter the Pinter. This can be resolved by gently leaning the Pinter over to one side to allow an air bubble to form in one corner. This should allow it to enter.