Yes it is. There is a breed of Papillion called Phalen, and their ears are not erect although can be when excited.
my papillion is the same way he is four and he has always had a droppy ear but it does go up when he gets excited
My pap had a drooping right ear until all his permanent teeth came in - now it is fine. Unless you bought him for a show dog, I wouldn't worry about it - they are wonderful companions and one droopy ear can be enchanting.
My 6th month old pap has HUGE ears and we thought they were never going to come up . Finally one came up and then they would switch.. one up then one down every once in a while. So then we tried taping. this is when you apply moleskin( a stiff material that is sticky on the back) to the inside of the ear. I have found that a triangle shape works the best on the ear. the moleskin should stay on the ear for about two weeks so it can make the ear stronger and then the ear should come up! my paps finally did ... and gues what now i am showing him in conformation. hope this helped!!!
He's probably a Phalene cross. (there are two types of Papillon) They have droopy ears.