WHMCS ResellerClub Issue with API Access
1.) Check that your IP is whitelisted in WHMCS
---> Login to WHMCS go to -->Setup-->General Settings-->API IP Access Restriction
Add your Primary Server IP or your Static IP here see what your whmcs use...
2.) Next make sure you have the correct setting under
--->Setup-->Products/Services-->Domain Registrars-->Choose Registrar Module: Resellerclub --> Add the correct ResellerID and Password here.
You can find the resellerID once you login to your ResellerClub account on the right you will see an human image next to feedback select "Manage Profile" from the dropdown and grab your Reseller Id:
3.) Next you would want to add your IP address to the API on the resellerclub.com account.
Login to your resellerclub account go to -->Settings-->API and under section:
Accessing the API - Specify the IP addresses from where you will make API requests. (IP ranges and netblocks are not accepted.)
Include your IP address and select --> Allow API Access
That should get you in and resolve your issues if not check whether PHP is compiled with curl (On cpanel you can go to SSH and run --> /scripts/easyapache configure easyapache with Curl options enabled.