Please note: These are general points, which apply to *any* application that uses sessions (e.g. for user login). They are not particular to simpleContact.
------------------------------------------
Session storage
In order to create a session, PHP must be able to create a session ID and save a session file (which stores information about application state) to a location on your server. This corresponds to a cookie (which also holds the session ID) that is stored by your browser.
iPage require that you add the following line of code to the top of your config file:
session_save_path("yourhomedirectorypath/cgi-bin/tmp");
Log into your control panel and see the PHP scripting page for the full path to your home directory.
Reference: Running PHP sessions (iPage knowledgebase)