Ex parte is used to refer to motions for orders that can be granted without waiting for a response from the other side. Generally, these are orders that are only in place until further hearings can be held, such as a temporary restraining order.
Nazarat report is termed as a survey report, where the government officials will conduct a survey of whether the summons have been received by you or not and also conduct survey on the working of the post. There is no compulsion for the Nazarat report but if the court has said and want a Nazarat report then you should not go against the order of court.
If the officials of the court think that it is not necessary to have a Nazarat report then they can pass an ex-parte decree without waiting for the Nazarat report and if they feel that this report is necessary for any proceedings further then they will wait till they get the Nazarat report by the government officials.
You need not worry about the survey the court must have said this because it cannot rely on the technical aspect of law. There can be any problem while tracking the receipt. It might want to confirm that you physically received the summons and have responded to it.
Reference: Civil Procedural Code