Plugin does not work anymore

If i select an image in the media library in WordPress 4.3 and want to try a force regenerate, the page will be opened and the progress bar is running, but in the output console on the page there are only listed numbers, like

1.
2.
3.

but without any description behind the numbers.
No error messages in the wordpress debug log and none in the php error log.
What’s wrong here?

https://ww.wp.xz.cn/plugins/force-regenerate-thumbnails/