Solid state relay not turning on motor as expected

First, take note that your SSR is drawn backwards in your schematic.

Most LED's are current driven devices that will illuminate properly with 10 to 15 mA of current. When this much current passes through the LED, it generally has about 2 volts across it. This means that you need a resistor that will have the other 22 volts across it when ~10 mA of current is passing through it.

A simple Ohm's law calculation of 22 volts / 0.010 amps shows that a resistor of ~ 2200 ohms should do the job. Then calculate the wattage rating of the resistor as 0.010 amps * 0.010 amps * 2200 ohms and you have 0.22 watts. For reliability sake, you should use at least a 0.5 watt resistor.

The LED is connected in parallel with the LED of your SSR with the same polarity as the LED in the SSR (recalling that your schematic shows it backwards).

The solid state relay you're using is designed for switching moderate current loads on and off, from a power supply, and not for switching signal lines.

Unlike a mechanical relay, your solid state relay behaves as if there were a diode in series with the relay contacts.

You can likely easily adapt it to do what you want but you'll need to understand in which direction the current is flowing in your existing circuit.

What's most likely is that the encoder signals to the camera by pulling the input to the camera low by connecting it to ground.

If that's the case you need to reverse the connections on pins 13 and 14.

It's also possible that your camera has a very high impedance input, and that you need to pull the camera input low or high as appropriate with a resistor to compensate for the leakage current through the solid state relay.