If a pilot calls or emails in with a problem connecting the IFD100 to the IFD in the a/c and it is not a WIFI issue, have them check SW version on both units. If the Jepp database or the SW version are different, it will have a hard time communicating.
A fix for this then would be to update the Jeppesen database on both units to the current 28 day NAV cycle. Also, the SW version of the APP and the IFD panel mount need to be the same (i.e. SW ver. 10.2.3.1).