We renamed some of the IIS webserver and .Net agents 2 weeks back. The old names still appearing in the OOTB dashlets , greyed out though . How long its going to be there ? Is there any way to remove them forcefully ? I confirmed that there is no open incidents against those old agents
Please check the host group settings: Open Server Settings -> Infrastructure -> Select Hostroups tab -> Open Default Hostgroup. Was the "Automatically remove offline Hosts" setting modified? It defaults to 72 hours.