When attempting to open activity center pages such as "Manage > Computers" or "Manage > Software" etc the console shows the jewel box outlines of the pages but nothing is in the boxes, they are completely blank.
There were no visible errors in the SMP logs, but when running Fiddler (www.fiddler2.com) when loading the Activity Center pages there was a 405 error being returned when it was attempting to access "/Altiris/ActivityCenter/Service/UIService.svc" or "/Altiris/ActivityCenter/Service/SoftwareService.svc"
As well you may get http error 407.17.
The underlying problem was that IIS was throwing a 405 "Method not supported" error in response--when attempting to load page "/Altiris/ActivityCenter/Service/UIService.svc"
In examining the Handler Mappings section for "/Altiris/ActivityCenter" in IIS there was no handler for .NET 4 64 bit POST requests.
ITMS 7.6, 8.x
Adding the "svc-ISAPI-4.0_64bit" script map handler, which was missing, eventually corrected the problem:
Note: As well you may need to add svc-Integrated-4.0 and svc-ISAPI-4.0_32bit
Request Path: *.svc
Note: This handlers mappings are installed by default during the initial installation for the Roles and Features needed for the SMP to install: