I have port forwarded and configured my server properly, but when I test the port, it still says it's not active while the server is running. In the cmd, it shows that the port 25565 isn't active as well.
First thing I would check would be your server.properties file. Stop your server before editing it though.
Look for the line:
If you have anything on this line after the = sign, try removing it - just leave it blank like above. Unless you have a good reason to manually force an IP binding, then Mojang recommends this line stays blank, but you'd be surprised how many people change it. See the Wiki, at https://minecraft.gamepedia.com/Server.properties#Java_Edition_3 for more info.
Also, if your MotD is incorrectly formatted, this can cause issues. Check it (usually the bottom line of the file), and if necessary, use an online MotD generator, such as https://minecraft.tools/en/motd.php
Finally, double-check the line:
just in case. Also ensure there is no space on the end of the line or something.
Next, check your firewall rules - both Windows Firewall (or a 3rd-party one if you have one) and the firewall/port forwarding on your router, to ensure your port is allowed through.
Also, connect to your server on all 3 IP addresses to check it. '127.0.0.1' or 'localhost' from the PC that the server is running on, your internal network IP (usually beginning 192.168.), and your external IP through your routers port forwarding (the one shown when you type "What is my IP" into Google).
I hope this helps.