-Very first step *do this first or "notifcations categories" wont show up in second step*
Settings > nonification > advanced settings > scroll down and turn on option,Manage notification categories for apps"
-then
After toggling that on- settings > notifications > app notifications, choose the app, "Notification Categories"- then at the top there are "Account activity and policies" click on them (not the slider, more to the left) then it should let you click sounds