In KSP 0.90 (beta), command pods only provide SAS when a pilot is onboard. A probe command pod like the Stayputnik doesn't have a pilot aboard. I tried adding an SAS module to my Stayputnik probes, but this doesn't enable SAS. How does one get SAS working with a probe in KSP 0.90?
There's a similar but obsolete question about SAS on piloted vessels in a much earlier version of KSP. How to get SAS working in Kerbal Space Program