Orlick loses his job at Miss Havisham’s because Pip tells Jaggers that he is an unsavory character.
When Pip sees Orlick at Miss Havisham’s house, he is not at all happy to see him there. He does not think Orlick is a good person. He is convinced that Orlick attacked his sister, and decides to let Jaggers know that Orlick is trouble.
I resolved to tell my guardian that I doubted Orlick's being the right sort of man to fill a post of trust at Miss Havisham's. (Ch. 30)
Pip immediately tells Jaggers, who seems to find the idea amusing and suggests that Orlick would not be at all difficult to deal with. Pip worries that Orlick would argue with Jaggers, but Jaggers is not at all concerned.
“I should like to see him argue the question with me.” (Ch. 30)
Seeing Orlick reminds Pip of his childhood, and his young self and older self collide. He still has some of his childish fears and reservations of Orlick, but Jaggers sees him for who he is—a common criminal. Jaggers can size him up immediately, and knows his type well. He would never be afraid of Orlick. He deals with his type all of the time. Most criminals are afraid of Jaggers, not the other way around. Jaggers demonstrates this confidence in his answer to Pip.
In having Orlick show up again in the story, Dickens continues to weave the web of the story. He wants to make sure the reader does not forget old Orlick. He also wants to give Orlick another reason to hate Pip. Losing his job at Miss Havisham’s is one of the reasons Orlick gives for killing Pip when he lures him out and tries to kill him later on. Orlick is as slimy as ever when Pip encounters him working for Miss Havisham, and his presence there further demonstrates her tendency to surround herself with decay rather than life.