Hi,
I had the same issue on 2.1.8. I had to disable password (Edit Options -> Advanced -> Ignore Password) before I could get API to return anything other than {result: 2}.
Also see: https://opensprinkler.com/forums/topic/is-the-api-working-on-firmware-2-1-3/
My password did not have any special characters in it.
Regards,
Francois.