Hi Phil,
connectx_port_config script doesn't support Connectx-4 , it only supports ConnectX-2, ConnectX-3, XonnectX-3 Pro.
For connectx-4 please use the mlxconfig tool:
for example:
mst start
mlxconfig -d /dev/mst/mt4115_pciconf0 s LINK_TYPE_P1=2
if you have a second port
mlxconfig -d /dev/mst/mt4115_pciconf0 s LINK_TYPE_P2=2
Reboot for changes to take effect.