Assigning Users to Security Groups in Maximo is a common task for most Maximo Administrators. What is important to remember is that Maximo provides an additional layer of access related to the Security Groups and Users application, named: Authorize Group Reassignment.
This functionality can be found in either the Security Group or Users application, under the More Actions menu, as shown below:
If you do not see the Authorize Group Reassignment option, make sure that you have selected an individual User or Security Group, and are no longer on the List tab of the application.
Clicking on this menu option opens up a dialog window, allowing you to select a list of Security Groups or Users, depending on the application you are in.
You should add all appropriate Users or Security Groups to this dialog window.
Tip: After adding a new Security Group, you often access the Authorize Group Reassignment from the Security Group application in order to associate each of your administrative users to the new group plus any non-administrative users that may need to manage this new group.
Tip: After adding a new Administrative User to your Maximo environment, you often access the Authorize Group Reassignment from the Users application in order to associate all of your Security Groups with your new user.
Further information available here from IBM.