When running Group reports, the Spectrum Report Manager (SRM) is not showing all of the Global Collections (GC) in the "Select the Global Collection" pull down.
Each SRM system is configured to monitor specific Landscapes. If a GC does not contain any members that are modeled in one of these Landscapes, then that GC will not appear in the list of GC's displayed in the "Select the Global Collection" pull down.
This is functioning as designed.