If you forget your WHMCS admin password and “Forgot password” does not send password reset link, you will need to reset it from your WHMCS MySQL database. Following are the exact steps:
 You must have access to your MySQL database.
 Backup your database before making any changes in the database.
 After taking the backup, access your MySQL database using the MySQL client tool provided by your hosting provider i.e. phpMyAdmin etc.
 Select your WHMCS database and locate the table “tbladmins“
 Locate the “admin” (or if you are using other username for admin locate appropriate user) row and click on “Edit” icon (if you are using phpMyAdmin, click on “pencil” icon.).
 Enter the new password in the “Password” field.
 Change the drop down menu to “MD5”.
 Now, click on save button.
Please note that if you have not reset your WHMCS admin password and it stopped working, you will need to investigate this further. There is a possibility that your installation is compromised. You can contact WHMCS support for further assistance and aslo make sure that you are using the latest stable released of WHMCS.