It will never work by connecting both directly together.
Your sensor is an open collector output (sink current when dry, max 40mA).
Your relay needs 12 tot 24 V to operate.
You need something in between sensor and relay...
I suggest that you try both seperatly first so that you get familiar with both systems.
Put a 1K resistor and LED between sensor output and +12V. Led should be on when the sensor is dry, off otherwise. (Watch the led polarity)
To operate the raley you need at least 9.6V, it will release when the voltage drops below 1V. Connect a switch between your 12V supply and the input of the SSR. When you close the switch the SSR must operate.
Now you know how both systems works, try to find a way to put them together. If it fails, post it here and we can help you further.
Why using a SSR?
Do you need the 15A load current of the SSR?
Why not using a standard relay?