I went back to kill the dragon to get additional gateways and after I killed the dragon no additional gateway appeared.  The first time I noticed that a couple blocks near my first gateway were destroyed, so I thought that might have caused an issue, but I went back and tried again and still no new gateway.  I'm thinking maybe my original gateway just keeps recreating and not in a new location.  I have seen others having this issue in newer snapshots, but my world was created in 1.19.3, and has only been updated to 1.19.4.  I have never opened the world in a snapshot.