Solid State Relay Voltage
When in its 'off' state, the SSR will still pass through a small leakage current. You can find its maximum value in the SSR datasheet.
If you have no load on the SSR output except a multimeter or oscilloscope, the very high input impedance of the DMM/scope will draw little current from the SSR. The leakage current will be enough to maintain a high voltage drop across the DMM/scope impedance. Hence the high voltage reading.
You don't say what your SSR load is.
Try connecting a continuous load, like a fan or light bulb, to the SSR output and measure again. You'll find that the small leakage current will be sunk by the load and you'll measure almost no voltage.