First, Make sure that you have restarted the timer service after adding the farm account to the local administrator group.
Second, In case, you have SharePoint 2013 SP1 with SQL Server 2014, you must patch your farm with a cumulative update in May 2014 or later to can start User Profile Sync Service.
Third, Make sure that the UPS service is not stuck on another server, it must run only on one server,
Fourth, Stop the UPS as mentioned at Restart SharePoint Service Application using PowerShell
Fifth, After Stopping the UPS, start it via CA, Make sure that you have opened the CA as administrator when starting the UPS again.
Check other causes for this boring issue at