My blog won’t send pingbacks

Hello.

I’ve linked multiple blog posts (including some on my own blog) and a pingback has never apeared in any of the posts I have linked.

I just tested pinging back https://www.quietearth.us/webtools/pingback-tester.php and it didn’t work.

Please help me.

By the way, I have successfully received pingbacks and (spam) trackbacks ;).

Any clue in where my problem might be?

Thanks!