Solid State Relay not working, am I mis-reading the data sheet?
You need at least 1 mA to turn o the optoisolatorn. Your 20k on its own would limit the current to 12/20000 = 0.6 mA which isn't enough. R2 is shunting some of the current that does make it through and stealing it from the SSR.

Try this (and note convention of + rail at top with current flowing from top to bottom of circuit for readability).







simulate this circuit &ndash; Schematic created using CircuitLab