Plesk reseller can't add server to WHMCS.

[RomanSangemino]

I sold a reseller package to one of my friends from my Plesk server, but they can't seem to add it with their login details to WHMCS.

I am completely dumfounded as I can easily add it to my WHMCS with the root user.

All WHMCS says is "Error", literally nothing else, even in logs nothing shows up.

 

Any ideas are greatly appreciated....