Add FAQ for router clients (#629)

FAQ.md

@@ -80,3 +80,16 @@ If your client is <2.3.3, remove `tls-version-min 1.2` from your `/etc/openvpn/s
 **A:** Iptables rules are saved at `/etc/iptables/add-openvpn-rules.sh` and `/etc/iptables/rm-openvpn-rules.sh`. They are managed by the service `/etc/systemd/system/iptables-openvpn.service`
 
 Sysctl options are at `/etc/sysctl.d/20-openvpn.conf`
+
+---
+
+**Q:** My router can't connect
+
+**A:**
+- `Options error: No closing quotation (") in config.ovpn:46` :
+
+   type `yes` when asked to customize encryption settings and choose `tls-auth`
+
+- `Options error: Unrecognized option or missing parameter(s) in config.ovpn:36: tls-version-min (2.3.2)` :
+
+   see question "Can I use an OpenVPN 2.3 client?"