Custom permalink 404 Error

same prob as well

Did you ever try switching to a non-custom permalink structure? If you switch to any of the permalink settings other than “custom structure” and your problems go away, then it’s an issue with the custom structure you’re using.

thank you bagel, i solve it by restoring the old wp core and update it manually, it works again, thankyou

Big Bagel! I have the same problem, and switching to a non-custom permalink structure DID fix it.

So now that I know it’s an issue with the custom structure I’m using, can I fix that?? Surely I can’t be doomed to the default settings?

What I’m using is just a plain old wordpress-suggested structure, the radio button they label as “month and name”. Everything was working fine before I migrated my site from a subfolder to the root folder.

Now the only thing not working is my custom post type. Everything else — the single posts, the taxonomy pages — works fine.

GOT IT. Thanks to AldebaranJill:

Just had identical issue and here’s the fix:
https://aldebaranwebdesign.com/blog/if-upgrading-to-wordpress-3-1-results-in-404-pages-not-found/

Had to do with disabling all plugins and regenerating .htaccess file and making sure all plugins were reenabled one at a time and deleted which one broke it. But needed new .htaccess file – so there were two issues – so just because you create new .htaccess file, be sure to make sure all of your plugins are not causing secondary issue.