Of course it appears but, of course, when an operator doesn't seem to appear when it used to, there's always a reason, for example somebody provided more accurate informations (or made a profile) about which operators are available on a given airport, so they might replace lower-scoring operators that only got there before because there was no better info.
So, if you just said WHICH airport you are referring to, and if you are using a GSX profile for that airport (that might have specified an explicit operator), it would be easier to explain it.
Reading the manual, Page 95, the Operators Assignment Rules chapter will help you understand how the scoring system works.