Before you attempt to troubleshoot the issue, make sure that the recipient's address is typed correctly and that any emails you are expecting haven’t been automatically filtered into a folder like Spam or Junk.

If the address is correct and you aren't seeing your emails, consider the following:

1. Check the email client for temporary difficulties
   It's possible that the email is having temporary difficulties. Wait a few minutes and try again.
   
2. Check the inbox for any changes that could have resulted in your messages being filtered
   There may have been recent changes to inbox settings that have negatively impacted your emails.
   
3. Check your message history
   If the address is correct and the message hasn't been filtered, check your message history to make sure they were sent properly.
   
4. Check if the recipient has blocked you
   Although this usually an unlikely option, it is still possible that the recipient has blocked your emails which would prevent them from being delivered.