It should activate relay output when you trigger digital isolated input. If you are choosing low level, first you will have to turn it to high level and switch it back to activate. With this input rule it works fine:
Also I would like to ask, how do you expect it to function. If you want relay output to activate, only when both conditions are met, it will not work. Output will be activated by last triggered input rule. For example if you get digital isolated input from high to low level it will activate relay output, but if digital input will go from high to low level a second later it will turn it of, and to turn it back on with Digital isolated input you will have it to go to high and back to low level again.