Edit record link in Customer Portal

Edit record link in Customer Portal

I have an application and I am using the following script on my form "Contact_Information" > on load:

(I have inserted <appuser> and <appname> in place of the correct code below)

record  =  Contact_Information  [Sponsor == input.Sponsor];
if (Contact_Information[Sponsor == input.Sponsor].count()  >  0)
{
    openUrl(" http://creator.zoho.com/<appuser>/<appname>/#Form:Contact_Information?recLinkID=" + record.ID + "&viewLinkName=Contact_Information_Report", "same window");
}

When I am logged in, this works perfectly and if the form exists, it will load it for editing rather than allowing me to enter a second form. 

However, when I try to access this when I am logged in as a user in my customer portal, I am taken to this link: 

I have checked and the permissions are set for my portal user to be able to edit, so I am not sure why this would be happening?