error 404 for POS page

I keep getting a 404 error when trying to load the POS page. Am using version 0.4.6 of POS and I have followed the instructions found at http://faq.wcpos.com/v/0.4.6/en/getting-404-error-page-not-found.html

I have also tried changing the permalink structure a couple of times to see if this makes a difference but without success.

Does anyone have any ideas on what would be causing this?

https://wordpress.org/plugins/woocommerce-pos/