***UPDATE: This document is related to version 1.0.0 of the Magento module, please update to 2.x.x of the module if you are still using it***
The default Magento URLs to enter into ICEPAY are:
http://www.mystore.com/index.php/Icepay/redirect/success
http://www.mystore.com/index.php/Icepay/redirect/cancel
http://www.mystore.com/index.php/Icepay/redirect/notify
www.mystore.com marked in blue should be changed to your own website.
A setting within Magento might alter the access to the ICEPAY scripts and as such those URLs would cause a 404 "page not found" error.
First check the Capital "I" on Icepay before proceeding any further.
The setting can be found under Magento Admin > System > Configuration > General Web > URL Options.
If Add Store Code to Urls is marked as "No" then the first mentioned URLs should work properly.
If Add Store Code to Urls is marked as "Yes" then the URLs should be changed to include the Store Code.
For example:
http://www.mystore.com/index.php/firststore/Icepay/redirect/success
http://www.mystore.com/index.php/firststore/Icepay/redirect/cancel
http://www.mystore.com/index.php/firststore/Icepay/redirect/notify