Is the IDM webserver running on the sensors?
If so, you should not use the idsupdate command line tool
to schedule updates.
If you schedule an update from the command line while the webserver
is running, it will be ignored by IDM. Then when the update is attempted
the file will be downloaded but not executed, because the webserver is
running. But the the webserver won't warn users of a pending update
since it is unaware that the update was scheduled.
If the webserver is running, all updates should be scheduled from
IDM Administration.Update page.