It's a common question, but I don't seem to be able to fix the issue by any of the methods outlined.
I've setup the plugin according to the directions and have triple checked those configurations.
I receive the error on the Default Content Page:
Sorry this doesn't look like a WHMCS site at [http://manage.datashrine.net/] Make sure your WHMCS Integration settings are pointing to the correct URL and that the WHMCS site is set for the Portal template in Setup | General.
Thanks for the help.