DIAGNOSIS Weak remote signal. Usually a depleted battery or an obstructed IR sensor on the unit.
FIX Replace the remote batteries (two AAA). Do not use rechargeables, their voltage is too low. Clean the remote's IR lens and the unit's IR sensor window with a dry cloth.
IF THAT DIDN'T WORK The remote's IR LED may be failing. Test by pointing the remote at your phone camera and pressing a button. You should see a purple light through the camera. If not, the remote is dead.
HEADS UP The IR sensor on the LP1419IVSM is behind the front panel display window. Make sure nothing is blocking it, like a TV or bright light shining directly on it.