Login with Session Token

Hi I am integrating the ESignLive SDK into an Android app. I already have a login mechanism (using username/password combination or using google sign in). I do not want to have an extra login for ESignLive. I noticed there is a method to login with session token. I have tried to get session tokens following the provided documentation(http://docs.esignlive.com/content/c_integrator_s_guide/rest_api/authentication_tokens.htm) to create "Tokens for Users". But when I use the result session token, I get an error "The provided session token is invalid". How do I generate a valid session token to use with Mobile SDKs?