Does not work
System
OS: Ubuntu 18.04.6 LTS (XFCE/xubuntu) Word size of OS: 64-bit Word size of FreeCAD: 64-bit Version: 0.19. Build type: Release Branch: unknown Hash: 7a9aa7edf2f44e3eb6a8e3e61c753368496b1399 Python version: 3.6.9 Qt version: 5.9.5 Coin version: 4.0.0a OCC version: 7.5.2 Locale: English/UnitedStates (en_US)
Problem
I'm using this video as tutorial, but on my machine nothing happens when I click "Add same faces" :neutral_face:
Demonstration

I am not an expert here, Just a suggestion Try a lower version of Freecad see if it works. I am also facing a different problem. I am suspecting this is a version compatibility issue.
System
OS: Ubuntu 18.04.6 LTS (XFCE/xubuntu) Word size of OS: 64-bit Word size of FreeCAD: 64-bit Version: 0.19. Build type: Release Branch: unknown Hash: 7a9aa7edf2f44e3eb6a8e3e61c753368496b1399 Python version: 3.6.9 Qt version: 5.9.5 Coin version: 4.0.0a OCC version: 7.5.2 Locale: English/UnitedStates (en_US)
Problem
I'm using this video as tutorial, but on my machine nothing happens when I click "Add same faces" neutral_face
Demonstration
Check the report pane.
With 0.19 I got
Part of face Face1 is not configured messages
Same here. v0.19
I had the similar issue.
What helped in my case was making sure that i selected the face of a geometry and not the whole geometry from the combinational view
example of full body selection

example of only face selection
click in the model on the face you would want to select

You do not use the tool correctly :
- Select both parts.
- Click "Add parts" or "Add same parts".
- Hide the left part (select it and hit "space" key)
- Select the face of the right part in contact with the left part.
- Click "Add faces" or "Add same faces".
- Select the added face in the tree
- Trim parameters (Number of tabs, width of tabs...)
- Click "Preview"
- Adjust parameters if needed
- Click "OK" when done