I posted this on the mozilla forum, but hopefully I can get a faster response here.

I'm hosting this on unraid as a docker. If I set sync server up on the local network, it works. I use this public address in the docker container http://localhost:5000 and the about:config server as identity.sync.tokenserver.uri = http://localhost:5000/token/1.0/sync/1.5.

Now if I switch to my reverse proxy (swag), I use this public address in the docker container http://firefox.mydomain.com/ and the about:config server as identity.sync.tokenserver.uri = http://firefox.mydomain.com:5000/token/1.0/sync/1.5. It does not sync. I get an error if I use that url in the browser link. If I make it http://firefox.mydomain.com/token/1.0/sync/1.5 (taking out the port number), my browser displays a json page. But if I remove the port number in the about:config and make it identity.sync.tokenserver.uri = http://firefox.mydomain.com/token/1.0/sync/1.5, it logs me out of my firefox account. It says the account is disconnected requiring me to login. If I do, I get booted out again.

The reverse proxy is passing through port 5000, so that is why not specifying it returns a valid browser page. The about:config seems to need the port specified to work. Otherwise I'm getting logged off. Is there a workaround to this?