Where are you expecting composite output? The Genesis 1 (and 2) outputs RGB, which gets converted to YPbPr by the HD Retrovision cables.
When you have the Genesis and HD Retrovision cables connected to the OSSC with its input set to AV2-YPbPr, what happens with the LED (does it stay red, green, flicker?), and what does its LCD say?
I wasn’t expecting composite. Just thought that was the output.
The OSSC says No Sync and the light is red. I assume this is due to the signal coming out of the Genesis being so poor.