large thumbnails (256 x 256) aren't being generated

I'm not sure if its my configuration or something else. Any ideas why i got only thumbnails with THUMBNAIL_SIZE_NORMAL (128 x 128) on my system?

filename = thunar_file_get_thumbnail_path (element_data, THUNAR_THUMBNAIL_SIZE_LARGE);

I want LARGE thumbnails, but only get the NORMAL sized.

They were not generated, ~/.cache/thumbnails/large is nearly empty (only a few old thumbnails found there).