For those upgrading from previous versions of Ty Package Tracker..

IF you made the optional edits as per the Ty Package Tracker v2.3 readme, you'll need to roll those changes back.

From the v2.3 readme file:

Optional: (These changes are optional and not required for the mod to work. These optional change will make navigating more convenient.)
/includes/filenames.php (1 optional changes)
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Change #1: (highly recommended - Making this change will allow your customer to track packages from the "My account" Page.)
define('FILENAME_ACCOUNT_HISTORY_INFO', 'account_history_info');
to
define('FILENAME_ACCOUNT_HISTORY_INFO', 'tracker');
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Change #2: (recommended - Making this change will allow you to access tracker page instead of the using the default order page.)
define('FILENAME_ORDERS', 'orders');
to
define('FILENAME_ORDERS', 'tracker');
You will need to reverse these mods to /includes/filenames.php and restore the defaults for these settings.