Failed to load notebook

Error Message

Attempting to launch ArcGIS Notebooks in ArcGIS Pro 2.5 returns the following error message:

Error:   
Failed to load notebook

Cause

The error occurs when the Windows Task Manager is unable to initialize ArcGIS Pro due to the following reasons:

• An antivirus software installed on the machine is blocking the initialization of the app.
• An existing third-party app is blocking the initialization of the app, for example, AppLocker.

Solution or Workaround

Depending on the cause, select one of the options below to resolve the issue.

Note:
Depending on organization security protocol, assistance from an IT personnel may be required for both options. 

• Add exclusions in the antivirus software. To do so, refer to FAQ: How do I troubleshoot ArcGIS Desktop performance issues related to antivirus software (exceptions)? and relaunch ArcGIS Notebooks in ArcGIS Pro.
• Add exceptions or create an allowed list of ArcGIS applications on the third-party app. For example, if a third-party app such as AppLocker is causing the error, refer to Microsoft: Add exceptions for an AppLocker rule to whitelist ArcGIS Pro on the application.
• If the above solutions do not work, uninstall and reinstall ArcGIS Pro. To do so, refer to ArcMap: Uninstalling ArcGIS Desktop products and ArcGIS Pro: Download, install, and authorize.