ISP Home Page Issue

When I initially installed the Comodo Firewall I was able to access the home page of my ISP with no problem but since I updated the firewall to version I can’t access the home page. I have to change my firewall settings to “Allow All” and then I can get to the home page. After I get to the home page then I can change the setting back to “Custom” and can browse the web without problem. How can I configure the firewall so that I can leave the security level set to custom and still be able to access my home page? Any help will be greatly appreciated; thank you.