I assume that you are asking what is wrong in the city of Thebes at the start of the play. If that is the case, there are a number of things wrong. In general, things are going very badly for the city and that is why the people want to find out the cause of the troubles.
Among the problems are plague, fires, and famine. These things have been killing people and animals and the city is in bad shape.
As it turns out, the Oracle and Delphi says that all of these problems are happening because the previous king, Laius, had been murdered.