Better use: Je n’ai pas reçu le colis.

This is one finite action. There is no duration.

Dont use je ne recevais pas. only in particular cases: Je ne recevais pas les gros colis (parce que ma boîte aux lettres était petite).

With entendre, you can use the two forms:

• je n’entendais pas. (I was not here, or other reason). It is a less frequent form, with more explanations.
• je n’ai pas entendu. (It is past – I haven’t heard). It is the most frequent form.

Participe passé is used for meaning something that occurred and finished (a finite action). Example : j’ai reçu le colis (I received it, done)
Imparfait is used either to describe a situation or to mean something that is still occurring or that we are not sure it is finished. Example : je recevais le colis (meaning either to describe a situation like “at this time, I received the parcel, and then…” or an unfinished or repetitive action like “I used to receive it”).
I hope it is clear enough.