GameDash supports running the panel behind Cloudflare's proxy with no loss of functionality. It is the usual way to keep your host's real address off the public internet, and it puts static assets on a CDN close to your users.
The origin address is hidden. Traffic reaches Cloudflare, not your panel host directly, which removes the easiest route to attacking it.
DDoS mitigation sits in front of the panel rather than on your own bandwidth.
Static assets are cached at the edge, which noticeably reduces interface load times for users far from your host.
That is the whole of it. GameDash needs no configuration change to run behind a proxy.
Proxy the panel, not your nodes.
Nodes serve game traffic, which is frequently UDP and always latency-sensitive, and the panel needs to reach a node's control ports directly to manage it. Putting a node behind an HTTP proxy breaks both. See Ports & firewall for what actually needs to be reachable and from where.
Restrict node control ports by source address instead — that gets you most of the protection without breaking the control plane.
The usual causes, in order:
cookie.domain still covers the names
you are serving — see
Panel configuration.