Everything is up-to-date. The Send To menu on Foreflight does not include anything related to the plane when I'm in the plane. I know it works because I use it with the FlightStream in my other plane, both sending plans to the panel and receiving them when I make a change in the GTN in that plane.
My typical source of trouble has been missing the fine print somewhere in the multiple thousand-page manuals for the avionics. While going through them once again, I found this in the G3X Touch installation manual, revision AN, page 2-14: "In an installation with multiple GDU 4XX dipslays, the Bluetooth connection to the tablet computer should be made to the PFD1 GDU only." I had connected it to the MFD as noted in my OP above.
Next time I fly, I'll try making that change and see where it gets me.