So, a heads-up for Single Use license holders moving to ArcGIS for Desktop 10.4
Here is an interesting rub I just had when doing a cleaning and fresh install of ArcGIS for Desktop 10.4-- Esri's installer did not upgrade the FNPLicensingService.exe -- and so failed FlexNet Publisher trusted storage license fulfillment exchanges. Was able to point the install to an active concurrent license pool, which worked (but the available license status panels in ArcGIS Administrator -> Desktop -> Availability were blank). Strangely also affected an new installation of CityEngine 2015.2 on the same system--so guess all local Esri, e.g. <Publisher><Name>ArcGIS</Name><Products>..., FNP services were affected.
