The state monitoring module for IIS failed to find the specified application pool. This will prevent the state monitoring module from providing the latest state of the application pool.
The most likely reason for this error to happen is if the application pool was recently removed from IIS and the discovery rule for application pools did not detect the change yet.
If you recently removed the application pool specified in the error message, no action is required. Once the application pool is removed from Operations Manager the next time application pool discovery rule run, you can resolve this alert.