Why am I not able to edit other User accounts that have a lower User role than mine?

In order to have the ability to edit another User account, your lowest User role in the entire Enterprise must be higher than or equal to the other User's highest User role in the Enterprise. 

For example, if you are a "Site Administrator" in fake Site but a "Staff" user in Test Site (same Enterprise) and the account that you are trying to edit has a User role of "Program Manager" in both Sites, since your lowest role is "Staff" and the other User's highest role is Program Manager, you will not have the ability to edit the account.