I'm having this problem with only one of my servers.
WHMCS can't create cPanel accounts automatically because of this error:
Module Create Failed - Service ID: 738 - Error: Login Failed
- 25/03/2012 19:19 - admin - 12.345.678.9
I've searched around a while looking for a solution.
I have all the server details correct (username password and hash), as I can log myself in from my computer.
I can login using SSL mode or not.
I've whitelisted WHMCS IP in CSF and cPhulk.
Any help is appreciated.