If I got this correctly you have renamed tpl_page_2_default.php to tpl_product-inquires_default.php...

Look at the defines (emphasis in red)

In the english.php file I did this:

define('BOX_INFORMATION_PAGE_2', 'Product Inquires');


In includes\filenames.php
line 62: define('FILENAME_DEFINE_PAGE_2', 'define_product-inquiries');

line 106: define('FILENAME_PAGE_2', 'product-inquiries');
Zen Cart can not now find page_2 I would add your page as
Code:
define('FILENAME_DEFINE_PRODUCT-INQUIRES', 'define_product-inquiries');
and
line 106: define('FILENAME_PRODUCT-INQUIRES', 'product-inquiries');
And as I recall there are 4 places that this needs to be cross referenced and you can use the admin > tools > developers tool > and search for one that exists to find the instances/files that it appears in