Roger is right.
SAP have solved the issue in SUM SP16 PL8.
Moreover, If minimum Host agent version is 721 SP3 and you have registered SUM tool with it then the SUM tool start link from browser should work.
Also make sure that SUM directory is located under \usr\sap\<SID>\ only.
You should move ahead with 'Next" after first screen with "The tool is not running"
Thanks
Divyesh
Sr. SAP Basis