diff --git a/FAQ.md b/FAQ.md
index ddda514..ddf2bb4 100644
--- a/FAQ.md
+++ b/FAQ.md
@@ -539,6 +539,10 @@ The controlled side works fine with UDP `21116` port, but it can not connect to
 
 Please check `Setting` -> `Network` -> `Id/relay server` on rustdesk client, and the the screenshot of `Settigns` -> `Key` on the web console. Need to confirm they have the same key (public key). 
 
+# Failed to secure tcp: deadline has elapsed: Please try later
+
+If you run `hbbs -k ...`, make sure the the value of `-k` is the private key rather than the public key.
+
 # Deploy RustDesk server in intranet.
 
 First you should set relay server with public ip (you need to fix NAT hairping problem to use public ip in intranet first) explicitly on "settings" -> "relay" of web console. Or you can set relay server (public ip) explcitly on controlled side (remote side, the device you want to control).