Permission to RUN workflow

hi

i am trying to restric a group of users only to run this paticular workflow, when they login to run they this issue when View message operator runs "Current user is not allowed to execute this flow. Flow UUID: 123456-XXXX" i am not sure what permission did i missed. 

ERROR

runID.png

I already granted the following privvlages to SERVICE_DESK 

GROUP.pngWorkflowPermission.png