1. No email sent to them even though settings in post forms has the send notification to author
When you set a form to send the email to the author it will send the email to the author of the post that is either created or edited with that precise form, not to the author of the container, where you put the form into.
2. To send an email to the author of the Post where you insert the Form to (container), you will need custom code.
You could, for example, update a Custom Field in the form (it can be hidden, but persisting field) with the email of the author of the container where you put the Form into.
Then set the notification to be sent to that field's email
Most likely, but I am not sure, you want to send the email to the author of the Post "Volunteer Opportunity" and not to the author of the "Volunteer Enquiry", which is what you are creating/editing with the forms in question.
Hence you would need to use the cred_save_data hook to add some custom code which:
- gets the current container author
- gets their email
- puts that in a new field you added before to Types, then to the Form with Toolset Forms (single line for example)
- after, the email notification is set to send to that field email value