For IFR certification a composite airframe needs a conductive (usually copper mesh) part in the layup, for lightning protection. Pipistrel are currently navigating this headache with trying to get the Panthers IFR certified.
Edit: I see Peter said the same in the OP :)
I’ve once seen a text (SA07-22) from Cirrus explaining that the 30 or so built „SRV“ models do not have this wire mesh in the composite and therefore are not able to ever fly IFR. This is also reflected in the EASA TCDS:
OTOH, I know SRV‘s in Europe that were equipped with IFR NAV units and converted/approved for IFR by the authority and are flying IFR.
