I've just had to go through my account settings (click avatar on the top bar) then down to preferences. Under content options everything for "and receive email notifications" had been unticked. Have ticked them all and shall see if I get any notifications now.When creating a thread you scroll down to select allow notifications by email etc.
Existing thread use the Follow button up on the top right just below your username/account details button.
New site layout and we are all still finding our way a bit.