Custom Post Type Display and works but But Blank Quick Edit

The issue looks to be associated with your mmd_member_track_columns_head() function. Instead of modifying the default columns, they are being completely overwritten, causing the Quick Edit functionality to stop working. In particular, the title key must be part of the array for it to work. Try something like this:

add_filter('manage_mmdtrack_posts_columns', 'mmd_member_track_columns_head');
function mmd_member_track_columns_head( $defaults ) {

    // Modify the existing columns, instead of overwriting them.
    $defaults['title']                             = 'Name';
    $defaults['mmd_member_tracking_workout_count'] = 'Number of Workouts';
    $defaults['mmd_member_memberships']            = 'Active Membershps';

    // Remove the "Date" column if you don't want it.
    unset( $defaults['date'] );

    return $defaults;
}

This code does a few things:

1. It retains the “Title” column to allow the Quick Edit functionality to work, but renames it to “Name”. This should also allow you to remove code for outputting the title from mmd_track_columns_content() since WordPress does this automatically.
2. It removes the need for the mmd_member_category column, since WordPress outputs the associated taxonomy terms automatically. This should also allow you to remove code from mmd_track_columns_content().

In general, I’d recommend using the functionality that WordPress already provides instead of rewriting it. Not only will this limit the amount of custom code you have to write, but it will also further ensure compatibility with future versions of WordPress.

I hope this is helpful. Let me know if you have any questions.