I am using QB Online, I found I neglected to click the Automatically Send Email in the Scheduling settings of the invoices that would not send.  Go into each invoice you want to set to recur and then Manage (Gear at the top), Set to automate in the Scheduled box in the Manage area of the invoice.  Once you set them to Automatically Send then you can set its frequency.

You should then see the invoice to be sent in the Recurring Invoices settings as pointed out to in the image in this string.  You can edit the recurring invoices individually in that area if you need to change recipient, service, pricing, etc.

You can see if the recurring invoice was actually sent under the far left navigation Sales -> Invoices -> Status

It is "intuitive" once you set up a couple.