"Where is the professor?"
Translation:¿Dónde está el profesor?
When you are talking about the position of something, the verb "to be" is translated as "estar" (and its conjugations).
Because it is talking about the verb Estar and Está is the conjugation for "Profesor" in this case.
I think your mistake is that you wrote "profeSSor" with two letters S, and the correct way in spanish is "profesor" with only one S.