There could be several reasons why you are not getting Alerts or notifications:
1) Check you notifications in My Account -> Notifications and see if the check box have a tick in them for the way you want us to contact you.
2) The organiser has disabled your user, you can check this in My Householde -> Select Household icon -> Household details and the Family & Friends section shows all the Family group for this household. If your user is not ticked then you need to contact the organiser.
3)You have withdrawn from helping, in this case ask the organiser to re-invite you.