Why is the current model broken or displaying a red 'x'?
There are two reasons that the model may appear as broken:
The model contains a tool that is not found on the system. This could have been caused by the tool or toolbox being moved, renamed, deleted or a tool that is part of an extension that is not installed.
The model contains a tool with a signature that has changed since the model was created. A tool's signature or usage is considered changed if a parameter is added or removed, if the parameter order is changed, or if any of the following parameter properties have changed: Name, Direction, Parameter type, Default environment name, or Data type.
Repairing the Model
Right-click the model, and select Edit. Opening the model causes it to repair the change. This may take care of the issue.
Verify the tool nodes or data nodes are broken and are marked with a red 'x' symbol. If a tool is broken, and shows the 'x' symbol, select an option below:
If the tool is a Script or System tool, double-click the tool to browse to find it, or delete it if it is no longer desired.
If the tool is a model, right-click and edit it. Determine why it is broken in the same way as described above, or delete it if it is no longer desired.
From the Model menu, select Validate entire model to validate all the parameter values.
Save the model and exit ModelBuilder.
Run the model. The red 'x' still appears on the model but it should now run.
Re-open the application, and the red 'x' should not appear.