Ceridian Payroll /w Linux Firewall

I am currently running Red HAt 7.3 using iptables SNAT. It works great with every Internet enabled application except the Ceridian Payroll Software which does submitions over the internet using port 80 and 443. I think I must be missing something asto why this is not working. I was wandering if someone could let me know what type of Firewall they are using if they have Ceridian Software and if there were any specific configurations changes they had to make?