Trim gauge issues

[Dylan R]

Hi, everyone. My first post here. I've just installed a trim gauge on my 2020 df30 (genuine Suzuki part). I've followed the wiring diagrams and I'm pretty certain I've done it right. Only it's not working. It lights up when I switch the ignition on, but it isn't showing any trim movement when I trim up and down. Does the engine need to be running for it to display trim angle as that's the only thing I haven't tried yet.
Apart from the two wires (w/y, b) all other wires are fed through from the tacho. Thanks.