skunk cleaner alway hiding

hey i got a skunk cleaner shrimp about 3 weeks ago and it has bairly being out...always hiding upside down under live rock ....nothing is trying to attack it and am confused why it seems to be hiding...i have 2 clownfish...1 blue spot puffer...1 blue tang and a 2 spot goby in a 90 ltr tank... and nothing seems to be aggressive towards anyone else thanx for any help