When we upgraded the primary hub's robot we are no longer able to login.
If you have another 7.91 robot working - simply copy the missing binary files over and restart the Nimsoft Robot Watcher Service.
Alternatively - simply reinstall the robot using the associated installer on support.nimsoft.com.
This problem is related to an empty PATH variable under the controller environment tab:
For future robot updates the variable should be removed prior to deployment, and re added as needed after deployment.