Trigger return spring is either broken or missing. Watch the trigger movement when you pull back on the hammer, you can see it "reset" forward then the firing sequence works when you pull the trigger again.
Photo I found online shows the mechanics to be exactly the same as a S&W. I circled the area in yellow, the trigger return spring is within the black square block. Best case scenario is the spring is missing/broken/not installed correctly. The worst case scenario is the buyer pulled the trigger one or more times while the side plate was removed which puts a lot of pressure on the rear retaining pin that holds the spring in. Without the side plate the pin is missing 1/2 its support and can shear off. You better hope that didn't happen.
Man I should open a gunsmithing business....