Error when requesting password reset email – wp authentication

Sounds like a server configuration problem, not a WordPress thing. You said you were using Rackspace? I don’t have personal experience with Rackspace but it appears that they have some known issues with the default PHP mail() function. See: http://feedback.rackspace.com/forums/71021-product-feedback/suggestions/1873281-fully-support-php-mail-function- http://www.joshuawinn.com/huge-email-delays-on-rackspace-cloud-sites-dont-use-php-mail/ The primary issue is that sending straight through mail() doesn’t authenticate the sender, using … Read more

Functions.php reverted to new one

You should not change anything in files inside wp-admin and wp-includes folder. All these files gets overwritten when WordPress is updated. The correct functions.php file is in your theme folder. full path to that file: wp-content/themes/YOUR-THEME-FOLDER/functions.php

Why when I instantiate wp_error in a validation method my user registration method stops working?

It seems you need to use $errors = new \WP_Error(); in your code, since WP_Error isn’t part of your namespace. I ran a quick test on my machine, using wp-cli commands: Using new WP_Error(): % wp eval ‘namespace PJ\NS\Test; $x = new WP_Error(); var_dump( $x );’ Fatal error: Uncaught Error: Class ‘PJ\NS\Test\WP_Error’ not found in … Read more