FPL not syncing

I'm running an IFD100 (10.3.0.2) on an iPad Pro (16.5) and an IDF440 (10.3.1.2) using a PilotAware Network (UK Electronic Conspicuity device a bit like Status) with both iPad and IFD as clients.  Frequency sync works fine, however, FPL doesn't mirror.  As I have confirmed NavData and Obstacle databases are identical on both IFD100 and IFD440, I'm guessing the problem is that the current S/W version for the IFD100 is behind the latest AViOS update to 10.3.1.2, but I've seen comments on here that suggest that others have made this difference in S/W versions work.  Does anyone have any thoughts on what else to check?  I have had this working under the previous 10.3.0.2 AviOS.