Warning: An existing WordPress network was detected fixed

How to fix Warning: An existing WordPress network was detected

While converting a WordPress single install to multisite, the following error notice was displayed at the Network Setup admin page.

the instruction in Network Setup page clearly stated that the PHP constant definition below should be placed before

in wp-config.php file and I was placing the code the end of  wp-config.php.


Adding the PHP constant definition above

fixed the problem.

If the solution do not work for you, performing the ritual below certainly will.

  1. Reset your wp-config.php file back to its original state, remove any MULTISITE references.
  2. Delete the .htaccess file or move it temporarily.
  3. Drop the following tables from your WordPress Database, use a tool like phpMyAdmin if you are not comfortable directly modifying table data.
  4. Log out and Log back into your site and initiate the Network Setup.
  5. Recreate the .htaccess file with the copy pasted data.
  6. Modify the  wp-config.php file, remember to paste those lines above the line where it says /* That's all, stop editing! Happy blogging. */

Source: Stack Overflow.