When you say in Sandbox, it is working, ensure whatever you have listed above are in line with Sandbox. Unless some settings are missing in test client, system wont behave like this. Also ensure that in WE20, you have to maintain both Inbound and Outbout profile for that partner. If still you face this issue, please google it with the same text, so that you will find lot of threads discussed here on the same topic. Take the inputs from there.
G. Lakshmipathi