This is most likely due to iDevAffiliate being installed on the same server as MemberMouse. For example, your MemberMouse site is installed on
http://yourdomain.com and iDevAffiliate is installed on
http://affiliates.yourdomain.com. Some hosting providers have a security filter in place where they don't allow cURL requests to be made from the server to the server itself. In order to be able to connect MemberMouse to an iDevAffiliate install on the same server you'll need to work with your hosting provider to remove this restriction.