Help on enabling Insert, move or copy worksheet in excel

Good day to all.

In one of my excel files, the sheet tab under the insert main tab is greyed out i.e. remaining disabled.

Cells, column and row tabs are enabled but the sheet tab is disabled.

Upon right click on the sheet tab in the bottom scroll bar the all tabs except view code and protect sheet are disabled.

I tried in the advanced menu in options tab under file but cant figure out to restore the insert sheet , move or copy sheet option.

Request help and guidance from anyone on this.