LT8640S

I have a design with two LT8640S devices.  They are set to generate 12V from a 24V input.  One is used to power devices on another board.  The other powers on-board devices.  The LT8640S for the off-board devices works fine and generates 12V.  The LT8640S for the on-board devices never comes up.  It generates 2.428V.  I verified that there is not a problem with the board by removing the inductor and attaching a bench supply.  Both supplies have identical schematics.  The LT8640S is set for FCM with a switching frequency of just over 1 MHz.  RT=40.2k.  Do you hve any ideas about what could cause this?