I spent the last 6 hours searching the forum reading advice and testing things to try to solve the problem with some torrents not downloading because of port 6881 and the red ball at the bottom because of this port. It's a super easy fix, but was not explained in any one place and I thought I might save someone else a ton of time in the future. So here goes my quick tutorial.
First, you need to open a port though your VPN (NOT YOUR ROUTER). AirVPN which is well supported has a simple page to use, pick a number between 10000 and 50000 and use it for both the Port number and local port number. This is a great first step, it will keep you from picking a port already in use.
Second, make sure the docker is stopped and open the rtorrent.rc file it should be located at appdata\binhex-rtorrentvpn\rtorrent\config.
On each of the following lines you will need to delete the # at the beginning of the line
On line 77 change the range of network.port_range.set = make the starting and ending number your port number from the first step.
On line 115 set dht.mode.set = on
On line 119 dht.port.set = your port number
Save the file and start the docker.
I hope this helps someone in the future.