Do you have your RCON port opened. Must be Rust server port +1 (not sure if this is true or just myth and you can use every port you choose) but just try to enable port 28016 in the firewall or rooter and portforward it then set it in the startup file and should works... Also do everything pookins said above.
Done it all still didnt work. I'm assuming it just doesnt work on Windows hosted rust servers because i switched on over to Linux due to the server start maxing out ram and seeming like it was having software issues with memory stablability. Now its all works on Linux just fine no issues what so ever.
And I have everything set up the same which makes it even more odd. But it's all working now. It was really odd. Not sure if it just doesnt like Windows or what. Lemme know what you think tho. It's very interesting to me. It maxed out when it would max out at 50% memory before. No plugins, no mods, 2500 map and it kept maxing out. but as soon as i ran it on linux its completely different and normal and everything is working a hell of a lot better. a lot more stable.