Updated FAQ (markdown)

FAQ.md

@@ -1458,6 +1458,30 @@ Fails with error 403 https://github.com/rustdesk/rustdesk-server-pro/discussions
 >
 > User: The VM is configured behind a proxy but the container was not configured to use the proxy.
 
+- Case 4:
+
+The [proxy](https://github.com/rustdesk/rustdesk/wiki/FAQ#proxy-for-pro-server) is not set correctly. If you run rustdesk service with systemd service, please set it in rustdesk-hbbs service. e.g.
+
+```
+#!/usr/bin/env bash
+set -e
+
+PROXY_HOST="proxy.firma.local"
+PROXY_PORT="8080"
+
+sudo mkdir -p /etc/systemd/system/rustdesk-hbbs.service.d
+
+cat <<EOF | sudo tee /etc/systemd/system/rustdesk-hbbs.service.d/proxy.conf >/dev/null
+[Service]
+Environment="proxy=http://${PROXY_HOST}:${PROXY_PORT}"
+EOF
+
+sudo systemctl daemon-reload
+sudo systemctl restart rustdesk-hbbs.service
+sudo systemctl show rustdesk-hbbs.service | grep -i Environment
+sudo systemctl status rustdesk-hbbs.service --no-pager -l
+```
+
 
 # Showing multiple remote minotors as individual windows
 https://x.com/rustdesk/status/1714199082640581039