@elmoret Could you connect it via CAN to a mainboard? Just to check it shows up.
@Polyneutron21 What "adapter board" are you referring to? Is this the "third party CAN board"? And by "works perfectly" do you mean it powers on? Because it won't be talking to RRF unless it's running RRF, which it won't be.
Your wiring looks correct from the (clone) 1LC, at least as far as the first plug: red is +5V, black is GND, white is CAN_H, yellow is CAN_L.
Note in your first post, you stated:
Then I connected the green (CanH) and white (CanL)
But the CAN wiring coming from the 1LC is actually white (going to white) is CAN_H, and yellow (going to green) is CAN_L. See the 1LC v1.1 wiring diagram here https://docs.duet3d.com/duet_boards/duet_3_can_expansion/duet_3_1lc_v1.1_wiring.png
Did you test the SZP in that plug? Beyond that, I really can't really tell what's happening with the wiring, as it's mostly out of focus.
Ian