That's because to "view post," you're viewing it as if it's a regular post on the front end of the site. The plugin is meant to be viewed on the back-end only. Since it's a custom post type, the settings I've put in for it are *meant* to disable it from viewing and indexing (therefore giving access publicly) on the front end of the site, which is why you're getting a 404... It doesn't exist to be viewed on the front end.
You can change that if you like, but unfortunately I'm currently on vacation for the holidays at the moment, and I'm responding from my iPhone... I don't actually have access to my files to tell you exactly where to change this. But off the top of my head, I know it's in the main file (instructions.php) and you want to look at the "register_post_type" function, and look att he array variables to set it to it'll be indexed, etc. But keep in mind, if you do this, when the public does a search, these posts will appear in the search results.
Another alternative would be to create a 404 page template with a condition that will allow you to see the custom post type, using possibly your current_user_can() status as an admin and a custom query to view the post from the front end, but that would also require a bit of plugin editing since the custom post type is set to *not* be queryable. (I'd also rather test that put first, actually, which I can't do until I get back to my office.)
I do not ever intend for the posts you create to be found on the front end of the site, so this isn't something I ever plan to "fix," since it's really against the grain of the actual intended use of the plugin. If you want your posts to display on the front end of the site, there's plenty of other plugins out there that will create custom post types for that purpose. However, if it's a feature that you think would be helpful to you as an administrator (to be able to see the post before you publish) I can look into the possibility when I return from vacation (in early January) and give it a go at testing it out to be sure it doesn't affect other important features. Alternatively, I can just look into removing the "View this post" button... That's actually something I've never really thought about, to be honest!