How can I correct About Us link?

In my sidebox, my About Us link is wrongly pointing to an invalid site: /index.php?main_page=FILENAME_ABOUT_US

It should be: /index.php?main_page=about_us
Thus, it's going to Page Not Found page.

I have manually going to /index.php?main_page=about_us and this page exists.

How can I correct this? I have been trying to fix this but I couldn't find a solution.. :blush:

FILENAME_ABOUT_US is the constant for the define 'About Us'

Usually displays the constant due to a mis edited or corrupt file

check that the single quotes were not omitted in the define file for about us

define('FILENAME_DEFINE_ABOUT_US', 'About Us');
If you require assistance in finding the file/path use the developers tool kit
https://www.zen-cart.com/tutorials/index.php?article=38
https://www.zen-cart.com/tutorials/index.php?article=39