FSM not detected after retrofit

[yellowcake]

Hi all! I'm having a little bit of a pickle with retrofitting an FSM to my 2018 V40.

After connecting everything and making sure I'm splicing in the correct spots for the CAN bus, the FSM isn't communicating. In VDash it's showing up red, as is the FLR, in other software it's just grayed out.

The used FSM for this project is from a used model (31660982, dealer checked for compatibility on my vehicle).

When checking connections between the FSM plug and CVM plug both CAN terminals, the ground terminals and the power terminal are coming up as a closed circuit. But somehow, there is no communication possible between the car and the FSM. Trying to learn the FSM to the CEM using VDash resulted in an error.

Does someone know where to look next in trying to complete this retrofit?

Thanks in advance