What one gray check mark really means
WhatsApp uses one gray check for 'sent', two gray for 'delivered' and two blue for 'read' (if read receipts are on). A message stuck on one check has not reached their device yet. Blocking is one reason; an offline phone is a far more common one.
Why privacy settings look like blocking
Profile photo, About, last seen, online and status can each be set to Everyone, My contacts, My contacts except…, or Nobody. Someone tightening these settings creates exactly the same view as a block.
Limitations on WhatsApp
- WhatsApp shows no block notification to the blocked person.
- Every individual sign can be caused by privacy settings.
- Who Block Me cannot check delivery status for you.