I studied the problem for several days before writing this post. Is the game using a different port for ping? How is this system implemented in a dedicated server? 10999 UDP port (from server.ini) opened on router. There are three providers, all of which have a fixed public IP. However, no ping is displayed through any of them in the public server table. External ports are closed for incoming connections for security. Opened only 10999 UDP
Router: Mikrotik CCR1009-7G-1C-1S+