Revit Fundamentals - Unable to load Assembly Code data

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The Assembly Code in Revit is for assigning a Uniformat code to the Assembly Code type parameter of model elements.

In some circumstances, this file can disassociate from a project or model and cause this pop-up when trying to map a Revit element. 

If this happens to you, follow these simple steps and get your Project back up and running.

1. Go to the Manage tab on the Ribbon

2. Expand the Additional Settings tool in the Settings panel

3. Select Assembly Code

Selecting Assembly Code will open the Assembly Code Setting window.

4. In the Assemble Code Settings window, select Browse

*Note: this post is not a tutorial on all the features of the Assemble Code Settings Window. Please v...

5. Locate the default "UniformatClassifications.txt," generally found in the ProgramData folder for your version of Revit.

Notes:

1. For <Version>, this depends on which version of Revit you are working from
2. For <Region/Generic> This depends on which templates and formats you selected to download with your program. 
3. For most users, setting your path to "At library location" will suffice

Default folder location

C:\ProgramData\Autodesk\RVT <Version>\Libraries\<Region/Generic>\