I'm no expert in the BASIS portion of the show, but checking current client configuration tells me that the ECC user is of type SYSTEM. Are you 100% sure that the password is correct as defined in the RFC connection? You should be able to test through SM59 on SLT directly, which would tell you if there was a problem with the connection from SLT->ECC.
Otherwise, maybe the user you are logged in as doesn't have the authorization or the correct roles are not assigned in SLT?
Regards,
Justin