Try restarting your router by unplugging it, waiting several seconds, and then plugging it back in. Then start your server.
You are not helpful... Trust me.
Go to Control Panel, switch to Large or Small icons, go to Windows Firewall, go on the left-side panel "Turn Windows Firewall on or off" and turn both off. Then try again. Don't close this window in case there's no difference.
Even with the firewall on and the game on permitted, I had --- ping. When I disabled it completely suddenly poof; it worked. I am pretty sure this would need a server restart so rather don't do this in-game anyway. Also keep that firewall window open to enable both again if that doesn't work for you. Though that's what gave me the fix with the exactly same problems.