Frothing aid isn't clean, wipe with a damp cloth immediately after each use so the milk does not dry and clog the frother, Frothing aid is clogged. Clean frothing tube with a toothpick or paperclip. Insert into the hole of the frothing aid. Be sure to remove the black plastic cover, Not enough water to when frothing. If the problem persist and your unit is covered under warranty, please contact your nearest dervice centre tohave your unit looked after.