Centrelink claiming there is no outstanding review following death

My husband applied for Age Pension and was rejected based on old income data - the decision was manifestly incorrect. He immediately applied for a formal review, and received an acknowledgement letter. Unfortunately he passed just over five weeks later, having received no advice at all about the review.

He was also charged excess home care fees from July to October, as a result of the incorrect income figure being used. This error was compounded by Centrelink when it issued conflicting letters at the September quarterly review, directly resulting in even more fees being taken by the provider. My husband was owed around $4.5k at the time of his death.

As executor to his estate, I asked for information on the overpayment and review. In a letter received today, Centrelink claims there were no active reviews underway! And they ignored my questions about whether the HCP overpayment should be pursued from them or the home care provider.

I have a legal obligation to follow up all monies owed to the estate.

Can anyone tell me if the death of a client voids an existing formal request for review?