When changing the coupon status from Active to Inactive the Dropdown Status form field auto sets to Active Coupons.
This makes the Inactive Coupons invisible. If you want to see the Red Active and the Green Inactive status when changing statused then simlpy follow the these instructions:
Enjoy

in catalog/admin/coupon_admin.php

find:

if ($HTTP_GET_VARS['status']) {
$status = tep_db_prepare_input($HTTP_GET_VARS['status']);
} else {
$status = 'Y';
}

Replase with:

if ($HTTP_GET_VARS['status']) {
$status = tep_db_prepare_input($HTTP_GET_VARS['status']);
} else {
$status = '*';
}

More...