Hi,
Since I can see that Layer Combinations differ between these two views, you should first check if the layer on which you've placed your walls has proper Intersection Group.
Layers assigned to Intersection Group number 1 join only to layers with number 1, etc.; Intersection Group number 0 doesn't join with anything, even with elements on the same layer.
Łukasz Pietraszko
ArchiCAD 26 PL, since AC20 | WIN 10 Home
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