would be really grateful if someone could tell what am I doing wrong.
(the credentials in test data are not real, I am trying to get response for Failure Keychain)
needs change to </> and change to <input.USERNAME> and <input.PASSWORD> no @USERNAME @PASSWORD
what do you mean by </> ?
I changed content to: {“login”:<input.USERNAME>, “password”:<input.PASSWORD>}
still the same error pops up 
interpolated mode isn’t possible to pick when operating on Raw content mode.
As you can see i have Content-Type application/json, so it should be raw, thus I can onlyt pick Variable mode (VAR) or fixed mode (A), there is no interpolated (</>).
Needs change to standard.