Under General > Page 404 you can change page 404 description and button title.

1. Disable Search – In page 404 there is search form that you can disable it.
2. Message – Page 404 description under title.
3. Button – Back to homepage button title.
4. Custom – You can create page and name it 404 and publish it.

• Custom 404 – Go to Dashboard > Pages and create custom page and name it 404 or page-404, then add your content and publish it, WordPress automatically will redirect your 404 to custom page.

To fix error 404 on post type archive and single posts, Go to Dashboard > Settings > Permalink and once save permalink structure.

• Still facing error 404  – Deactivate all of your 3rd party plugins and only keep activate theme plugins, then again save permalink structure and check your portfolio pages. If still have them same problem, You need to delete your server .htaccess file and try saving permalink again. Finally if still have same problem, you need to contact with your server support.

XTRA theme automatically will detect your custom page 404, Go to Dashboard > Pages > Add New and create a new custom page and set its slug to 404 or page-404 then add your content and publish page or save it as draft.

• Default 404 options  – Go to Theme Options > General > Page 404