Responsive Image Module is only selecting fallback image style
The posted responsive image configuration seems correct. Remember that you also need to change the image field formatter to "Responsive image". If you are using image fields on node entities, you can do this at

/admin/structure/types/manage/MY_NODE_TYPE/display/MY_VIEW_MODE

(If you are using image media entities instead of image fields, use the "Rendered entity" field formatter on the node, and switch to the "Responsive image" field formatter on the media entity at /admin/structure/media/manage/MY_MEDIA_TYPE/display/MY_VIEW_MODE )