I ‘Grouped’ my list ‘Announcements’ list ‘By’ categories and it works fine in the Announcement app but it does not display the grouping when I add it to a web part. How can I display the grouping in a web part?
When you customize the view for a web part, it creates a hidden view on the list that it is associated with. As suggested, you can edit the view on the web part and add the grouping. Since you mentioned that you already modified the view on the list, why not just change the view on the web part from Current View to your grouped view on your list? This will clone the grouped view into a new hidden view (thereafter it will show as Current View in your web part settings.)