Tank Auth: Account Confirmation Email Activation Code Expired

Question

When user click on "Finish Your Registration" link, it shows The activation code you entered is incorrect or expired.
Here is tank_auth configuration:

$config['allow_registration'] = TRUE;
$config['captcha_registration'] = FALSE;
$config['email_activation'] = TRUE;
$config['email_activation_expire'] = 60*60*24*2;
$config['email_account_details'] = TRUE;

It was working fine when I was using the original TA views. Not sure where and how to debug.
Codeigniter v2.1.2, PHP 5