Hi, Yes the tick box is checked in the Youtube app (Settings>General>Notifications).
Is your second suggestion on the S4 handset settings? Settings>More>Application Manager>Youtube>Show Notifications? Then yes that is checked too (i though that was more for app updates?)
The tick within the app itself has always been checked, which I just happened to noticed the other day and I thought it would be cool to get push notifications when a new video is uploaded to my subscriptions. Yesterday i did try the subs manager you mention and that does work but i don't want an email really, an alert on my S4 would be preferred.
Thanks.