They need to connect to one of the relays you send your notes to. I can see this note from primal.net and bitcoiner.social

You can go to your settings and add more relays to post your notes to if you think people aren't seeing them 

 Can you see any other notes from him? 
 

 I only see 2 notes in his history  

 I see only second one... Can't see the one with YouTube link (iris nor amethyst and have same relays in list you mentioned...). Tracking link could be a culprit? 

 The two notes I see are the one I replied to and one with a YouTube link to a mine craft video