The above link is working to me without any issue.

This issue maybe caused by corrupt cookies or cache. So therefore,
   Clear the Cache and Remove Cookies
   Type "about:preferences" and Enter in the address bar.

  To remove Cookies; Select Privacy & security. Then scroll down to "cookies and site data". Then press the button on the right side called manage data. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.

   To Clear the Cache; Press the button on the right side called Clear data.Then tick cached web content and then press clear button

See also to discussion in this thread.

• https://support.mozilla.org/en-US/questions/1267749#answer-1270378

Do you still have this problem with content being blocked when you disable Tracking Protection for this web page like I suggested in that thread ?

Note that you only disable Tracking Protection for a specific domain and that it is still enabled for other websites.