are you using the original product column in your detailed table or the new grouped column?
I am using one sheet as subcategory wise sales, and another as detailed table
There are two subcategory starts with 'A', So i clubbed them together and named as 'A'
and it works after action filter
Please check which column are you using in your detailed table.
Or please attach your workbook
Correct me if I've misunderstood your requirement.
Lets assume you've data like this
Product Sales (Grouped)
And Product detail , your dashboard action will act properly when you'll put the grouped field in detail shelf
then create dashboard action using your grouped field like this
so when you'll select grouped product "A" your action will show only associated product details in your view.
Let us know if this help.