After migrating SGK V2 to another project or large changes to the project the collision settings can be changed if your project has other collision settings in a different order to the clean SGK V2 project. These are the places to check after migrating if your building system isnt working correctly.

If you followed the migration video you should have these collision settings in your project setting but if you dont you must add them.

Below these are the settings of BuildPreview preset.

Below images are the setting your BP_PlayerBuildingComponent should have in its Class Defaults.

Below are nodes that you should check are set like the images, locations at the tops of the screenshots.

Note in newer versions you may have a Grid Channel variable plugged into the Trace Channel pin, in which case you can select the Grid Channel variable and in the details panel make sure its set to Grid.
This was added in a resent update if you do not have these nodes you can skip the image above.
This was added in a resent update if you do not have these nodes you can skip the image above.