000819: The tool is not available or is unassigned

Error Message

When running a script tool in ArcGIS Pro, the following error message is returned.

Error:
000819: The tool is not available or is unassigned

Cause

This error occurs when the script tool is labeled incorrectly, or the path to the source of the script tool does not match.

Solution or Workaround

Ensure the path to the source and the name of the script tool are correct. Complete the steps below to do so:

1. In ArcGIS Pro, navigate to View > Catalog pane.
2. In the Catalog pane, right-click the desired script tool and click Properties.

3. Copy the path link of the Toolbox.

4. Search the copied path link in Windows File Explorer.

5. Ensure the script tool name and path are correct.

The image below shows the script tool is completed successfully.