The tool references another tool that is no longer valid. Invalid tools will show an invalid tool symbol, invalid script, or invalid model. The tool either cannot be opened or does not exist. Some causes of this error include the following:
- A model may be using an invalid tool or may use another model that cannot be found or is invalid.
- If the tool is a custom tool built by a third-party developer, the tool may not exist in a toolbox, may have a problem with the tool's implementation, or may not have been registered appropriately at the time it was shared.
Sometimes editing a model and immediately saving it will fix problems with parameter changes.