customer invoice email link requires login

Sorry, but I am brand new to this plugin.
There is something I don’t really understand.
A customer receives their invoice with a link in it (of course they are instructed to click the link).
In my case, this link opens the website to the “Payments” page with the shortcode [wp-invoice] displayed.
Very confusing to a customer.

Now if I am already logged into the site and I click the link in the email, I get a new page showing my invoice and options.

SO, the real question is WHY does the link act this way (page with shortcode) if a customer is not logged in.

I have never seen this before in any actual private or retail sites.
It should be that when you click the link, if you are not logged in, it takes you to the login page and then once logged in, displays the invoice page.

The link action of just taking you to a page that displays the shortcode makes no sense to me at all.

Am I doing something wrong or is this the way this plugin is actually supposed to work?

Someone please help as I need to show this to my clients Monday morning (5-2-16) 8:00 am EST.

Thanks in advance…

https://www.ads-software.com/plugins/wp-invoice/