For those who may not be familiar, Sentinel is a software licensing and activation system developed by Flexera. It's commonly used by software vendors to manage and protect their licenses.
Add an exclusion for the port (the default port for Sentinel traffic). sentinel key not found
Most Sentinel USB keys have a small LED. If the light is off, the key isn't receiving power or is physically dead. For those who may not be familiar, Sentinel
Here are some possible causes and solutions: sentinel key not found