Check in the controller.log files ($installpath/Nimsoft/robot/*) - do you see any errors? Very often, the controller probe will provide some information on why the probe can't start.
What about the cdm.log - do you see any errors other than 'max restarts'? Raise the loglevel to 5 - does that add any information?
You might want to consider opening a ticket with Support should you not see any obvious errors.
Hope that helps!