Oups,
After watching the correct one, yes in “Monitor Administrators ACL”, I have these ones allowed :
local\Administrators
local\MonitorAdministrators
system/My webMethods Administrators
In which menu of MWS do you verify the “Central Users” schema used for monitoring please ?
When I click on menu “My webMethods\system parameters\servers”, all is displayed without any error (please see the picture above).
Ok, for the UM, I just wanted to be sure 
Regards
#webMethods#webMethods-General#Integration-Server-and-ESB