I recently logged into an SSAS server and was unable to add a user to the server security. Worse yet, the Security Properties tab was not showing domain user names, just SID’s. This means the service has lost connectivity to resolve SID’s with the domain.
The solution today was to run SSMS as Administrator, domain admin that is. Once connected the domain administrator account is able to remove the disconnected SID’s and add back the proper accounts.
On other occasions I have seen the security tab empty, meaning there is no recognized administrators. To resolve that issue, stop the service and edit the msmdsrv.ini file. In that file, you can set the property BuiltinAdminsAreServerAdmins which will recognize admins on the box as admin on the the SSAS Service. After a service stop/restart you can add/edit/remove admins using SSMS.
For more info about that, see MSDN.
Sometimes I blog these things just so I will remember it a few months from now. Hope this helps you too.
-Allen