SSS is officially supported on GPU in Blender starting with version 2.72. However, it's included in the 'experimental' kernel, not in the 'supported' one. If your project uses SSS and you want to render it on GPU, please launch the job from the Web interface and select the 'Experimental' feature set . If you uploaded the job using the plugin, please clone it to create a new job and select 'Experimental' for the new one.