By "turned this into a global report" I presume you mean you clicked on Tools | Organizer and, on the Reports tab, copied the report from your project to Global.mpt.
(You didn't actually say that so if you did something else, you'll have to be more specific in your description.)
This will work if and only if everyone is using the same Global.mpt. Depending on how your Project installations are performed this might (or might not) be the case.
Try putting the report back into the project file and tell everyone to open the file and use the report. If you want them to use that report for all projects then each of them should also use Tools | Organizer to copy the report from the project file to Global.mpt.