Unable to use the API connection from WHMCS to login to Reseller accounts.

Symptoms

Attempting to use WHMCS Single Sign-On returns the following error:

Action Failed Unable to auto-login. Please contact support.

The cPanel error_log returns the following error:

info [xml-api] You do not have permission to create sessions for the user “USER”. [create_user_session] version [1].

Description 

WHMCS is expected to manage the server for root and perform root actions. However, if the API token used to manage WHM doesn't have the "all" ACL, some actions can fail. WHMCS Single Sign-On expects the configured Token for WHM to have root privileges ( all privileges ).

Workaround

Ensure the WHM root API token being used in WHMCS has all privileges for root.

Then click Save.