Description
In the validation process for a model in ModelBuilder, ArcGIS confirms that it can set the output properties (such as cell size, extent, and mask) from each process. This information is then passed to the next process. In your situation, one or more of these output properties cannot be set. The model will not validate and therefore will not run.
Solution
Examine the input, output, and analysis properties for each process and ensure they are set to valid arguments.