After building a WordPress custom front-end user profile, inserted the generated shortcode into a published page, we still need to inform ProfilePress about the page that contains the profile shortcode so it knows what page to use in rendering the front-end profile.
If this isn't done, users profile won't be accessible via the url
http://yoursite.com/profile/username where http://yoursite.com is your website username and username is a user's username.
See the succinct guide below on how to get it done.
Under Front-end Profile Settings section, select the page with the profile shortcode in Page with User Profile Shortcode and save.
Finally, flush the rewrite rule by navigating to Settings > Permalinks and clicking the Save Changes button.
When the profile url (http://yoursite.com/profile/username) is visited, ProfilePress will used the page that was set above to render the profile page.
To redirect WordPress author page of users to their front-end profile, tick the Convert Authors to Profile checkbox.