Is court notice for the land which was sold years ago still valid?

My father had brought a land about 35 years ago from the plot owner and recently he sold it, a couple of years ago. The successor (grandson) of the initial plot owner had now sent a court notice claiming the plot ownership even though he is aware that my father had sold the said property. 1. Need the legal opinion if this notice still holds any value as my father is currently not the rightful owner of the property 2. What should be the response to the court notice to inform that my father no longer holds this property anymore Appreciate the feedback and recommendations