This works for me:
var btnElem = document.querySelector('div.fanyaTask div.bnt_group a.jb_btn');
btnElem.click()
based on an OCR of your HTML image, which could contain errors.
If this does not work, please post a broader range of HTML from your web page using Code Block.
Make sure the HTML contains enough UI elements so we can test run/view in a browser.