Ok, install your WP Integration plugin once again to try get around the issue with the other one.
Plugin is active.
Portal theme selected but have removed breadcrumbs from it.
Permalinks set to Post Name.
In the plugin settings:
Full url to WHMCS with trailing /.
New page created in WP called WP Int with [wcp_content] in the content.
Url to encode: domain.com/wp-int/ without http://
Not using https at all.
Viewing the WHMCS install /email/ I can see the Portal theme selected.
On the /wp-int/ page I still receive the following:
"Sorry this doesn't look like a WHMCS site at " error.
Please let me know what you'd like to look at.
Thanks in advance