- Do you have a toolbox directory on your program install folder?
- E.g. I have a 64-bit ArcGIS installation, so my toolboxes would be here: "C:\Program Files (x86)\ArcGIS\Desktop10.2\ArcToolbox\Toolboxes"
- If your answer is yes to #1, then did you add the toolbox library to your toolbox list?
I've found that when upgrading from an ArcGIS version (in my case, we went from 10.1 to 10.2) some of my ArcHydro Toolboxes went missing, and thus, my ModelBuilder routines were invalid. After repathing to my toolbox directory, the problem was solved.