I had this issue today, I was unable to login to my wordpress site. I first thought that “in some way” the password was changed (like that time that I ask “lastpass” to generate new passwords) but still with the new password I was unable to log in.

I made the change in database directly, then used wp_set_password (‘password’, $ID) in wp-themes/theme/functions.php with no luck :-(.

The problem was pretty… baffling, there was a plugin conflict that prevent me to log in to the admin area. 

I think login to the admin area should be one of those things that you should be able to do no matter if there is a plugin error, and those errors which should not be able to ‘crash’ the site in any way.

So, if you have  similar issue, not being able to login to the wp-admin area even if the password is correct try this:

1. Login to the server in a way you can handle files (FTP, Webdisk, SSH)
2. Go to your wordpress installation, more precisely to the wp-content folder.
3. Move/rename the plugins folder, let’s say plugins.bkp
4. Login to your wordpress wp-admin area.
5. If you were able to login, then go to the plugins area, you’ll see a bunch of notifications about every plugin that was active now is deactivated because the lack of the files.
6. Now move/rename the plugins.bkp folder back to ‘plugins’.
7. Reload the plugins page
8. Iterate over every plugin, one by one, until you discover the one that is in conflict.
   1. You’ll know that something is wrong with the plugin activation, in my case there was an “Are you sure?” question page, and after hitting “YES” the plugin was not activated, I had to repeat the steps 3-7 and avoid that last plugin (one before the one that raised the “Are you sure?” question.

I hope this works for you and saves you some hair and time.