Fix this up

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/VelocityServerConnection.java

@@ -94,6 +94,9 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
                 new LoginSessionHandler(server, VelocityServerConnection.this, result));
             startHandshake();
           } else {
+            // We need to remember to reset the in-flight connection to allow connect() to work
+            // properly.
+            proxyPlayer.resetInFlightConnection();
             result.completeExceptionally(future.cause());
           }
         });

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -286,6 +286,10 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     return connectedServer;
   }
 
+  public void resetInFlightConnection() {
+    connectionInFlight = null;
+  }
+
   public void handleConnectionException(RegisteredServer server, Throwable throwable) {
     if (throwable == null) {
       throw new NullPointerException("throwable");