A web consulting agency recently took over my admin account essentially locking me out of a website. Fortunately, if you have access to the database via a tool like PhpMyAdmin, you can easily get back in.

First open the wp_users table for the WordPress you wish to access. Look for your account and note down the user ID number:

Note: If you don’t have an existing account, you will need to create a new one. (You can check this article on how to do it.)

Next, access the wp_usermeta table and look for your ID number.

In the meta_key field wp_capabilities,
add this meta_value: a:1:{s:13:"administrator";s:1:"1";}

Save and exit and you should now be an administrator again.

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More info: https://themeisle.com/blog/new-wordpress-admin-user/