Just expand on Chris's answer - he's right.
Some functions on certain lists don’t work if your default view is grouped, sorted or filtered. Case in point: in the Tasks web part, if you try to indent tasks in the filtered view (i.e. My Tasks) – you will get the following error message: We can’t modify hierarchy on a view that is sorted/filtered/grouped.
As a result, don’t change that default view in SharePoint. If you decide to view information differently, you should create your own custom views.
https://sharepointmaven.com/dont-change-default-view-sharepoint/