In the affected computer, do the following: 

• go to Start -> Run… -> type regedit, then hit Enter
• browse to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Controls Folder\PowerCfg
• Right click to GlobalPowerPolicy and PowerPolicies, then choose Permissions…, tick Full Control under Allow column for Power Users and Users

Note: no need to restart the PC to take effect, just log-off as administrator and try it using the users' login details.