There is also a YouTube video tutorial on this topic made by us.
https://www.youtube.com/watch?v=EfOWIkypzco
FreePBX Password Reset
Sometimes it can be very frustrating when you lose one of your passwords, especially when it happens with your FreePBX. In this tutorial, I will show you in detail (with screenshots) how to reset FreePBX WebGUI admin password.
1. Go to https://yourFreePBX-IP/admin/config.php
2. Every web session in FreePBX has it’s own unique session ID, which we need to figure out in order to unlock our system.
Press Ctrl+A or start selecting text on the page with mouse cursor like on the screenshot below, to find out your current session ID.
3. SSH to your FreePBX system by any convenient method and change user to root (or SSH as root, if it’s allowed on your system).
4. Now run this command (as root!), as per screenshot below.
fwconsole unlock YOUR-SESSION-ID-HERE
5. Go back to your browser window and refresh the page (don’t open a FreePBX WebGUI in the new tab, or a different browser now, because session ID would be changed!).
You are now logged in to the dashboard as a fwconsole user. If you want to confirm this for yourself, please see the screenshot below.
6. Now when we are logged in, lets go ahead and reset the admin password, so that next time standard web form login can be used.
Go to Admin -> Administrators
7. On the right side of this page click the icon highlighted on the screenshot and then on the username you want to reset password for.
8. This would be the last step for this tutorial, I promise 
On the page presented to you, type in your new password and press Submit.
At this point everything should be okay. Logout from fwconsole account and try logging back in with your usual admin credentials.