You seemingly haven't installed it from its RBZ.
If you simply copy the ../Plugins/HouseBuilder_extension.RB file over to the newer SketchUp version it misses the images to make the toolbar-buttons [and worse!]...
Unfortunately the original author was in the dim past [20years ago] and made a half-baked extension loader file, and he didn't give his subfolder the same name as the RB file.
The new[ish] auto-migration tool assumes this file/folder naming convention and so it misses out copying the subfolder of images [and some other vital support files that are in that folder].
To fix it you need to find the whole HouseBuilder folder [and its contents intact] in your older version's Plugins folder and copy that whole folder over into the newer SketchUp version's Plugins folder.
When you startup SketchUp it should now find the subfolder and load the buttons' images and the other vital support files...