Not again!
An exclamation of anger, frustration, or exasperation about something bad that has happened again. Oh, not again! I just fixed that leak yesterday! A: "Hey Dan, the network crashed this morning." B: "Not again!"
Not again!
Inf. I cannot believe that it happened again! Mary: The sink is leaking again. Sally: Not again! Mary: Yes, again. Fred: Here comes Tom with a new girlfriend. Sue: Not again!