Try using port checker to verify if the port is actually open, if it is closed then the router’s ports are not opening like they should. I used to have this issue while back, my router is a Netgear Nighthawk R8000 model and through a software update I lost all port forwarding and UPNP functionality. I ended up flashing it with DD-WRT software and havent had an issue since. Apart from that, in your server settings, under custom command line arguments, type in -publiclobby and check to see if make community server is also enabled. I couldnt find my server without having both of those on.