Not able to edit or add new notification in notification plus. Error that comes up is RC Api error Resource parameter (subsciptionID) is not found

If you want a better chance for getting help here on the developer community, then put a few lines of codes (without any sensitive information such as a real phone number etc.) around the area that causes the problem in your question. With such a vague question, I can only tell that the subscription id you used in your code does not exist.