I installed and activated the plugin.
I am following the video on how to set up portfolio.
I click on Portfolio Items > Categories List.
I then click Add New OR Add a New Category.
The page refreshes and I get a page that looks like my website's theme that says Page Not Found.
There is also a bunch of widgets (Categories, Recent Pages, Posts, Recent Posts...) that would be visible on the front end, below where is says Page Not Found.
Any help is appreciated.