Upgrade to 4.0 and single-{Post_Type}.php get 404 Error

We have the same problem here.

If you set…

'hierarchical' => false

…on the register_post_type arguments, that should fix the problem.
Seems like hierarchical custom post types broken in WordPress 4.0.

There isn’t anything mentioned in the release notes regarding this though.

Here is a discussion someone posted yesterday as well regarding this: https://stackoverflow.com/questions/25740115/post-type-hierarchical

Does anyone know if this is a bug or if there is another solution to it?

Thanks for the response.

I’ll give it a try and see if it fixes our problem, otherwise I’ll wait and see if there is a more general solution.

You need to use flush_rewrite_rules(); after call register_post_type(…) for your Custom Post type.

@eugenyh

Yes but just once, not each time.

flush_rewrite_rules() is very resource intensive, see here: https://codex.www.ads-software.com/Function_Reference/flush_rewrite_rules

@tribulant Software

Thank you for your correction!
Of course, best way for production site – use it just once, as example, after theme activation.

Thanks for the response. I don’t know if this would have resolved the problem or not. When WordPress 4.0.1 was released, the issue that was causing a problem for this website was resolved and I was able to upgrade to 4.0.1 and then 4.1 with no problems.