On December 6 2018, WordPress 5.0 was released and with it came with the new WordPress editor known as Gutenberg.
If you’ve upgraded your WordPress site to this version, you would have noticed that the
wp.me shortlink for each post is no longer accessible next to the post’s permalink.
To find the shortlink for a post, you now have to click the green Jetpack icon at top right to open the Jetpack sidebar :
You’ll then see the shortlink url under the Shortlink section, where you can copy it to your clipboard: