Forward slash / between the default page and the endpoint slug is missing...

Forward slash / between the default page and the endpoint slug is missing which breaks all integrated links and generates 404 error pages.
Renders as .../portalclient/?
Should be .../portal/client/?
It seems that usage instructions were followed correctly and all links match as they should. We are using WP 3.7 and WHMCS Wordpress Integration 1.2.0.9. Any ideas what we may be overlooking that would cause this? Thanks!