Step1:
Goto SAP----> su01 transaction-----> give your username---->press F8---->again goto authorization tab----->check your username has a valid role to access services or not.
Step2:
While passing username and password to service, make sure this username and password is valid or not in gateway system.
Step2:
If valid---->go to console ---->network tab---->response tab---->copy the entire response---->post it here.
Regards,
Karthik A