sip_poke_noanswer peer is unreachable

I read the thread about a peer being unreachable. My situation is similar but did not really make out what the user did after all the posting.

Presently,

Asterisk server
TDM400P card
Analog phone plugged in and works inbound/outbound
Behind NAT
Ports 5060; 10000 & 20000 defined
x-lite installed
grandstream phone with dynamic ip address
Read Asterisk, SIP and NAT at voip-info; setup accordingly
simple basic sip

[general]
context=default
allowoverlap=no
bindport=5060
bindaddr=x.x.x.x
srvlookup=yes
allow=all

[1000]
type=friend
username=1000
host=dynamic
context=internal
dtmfmode=rfc2833

Start Asterisk ----> CLI and receive the following

sip_poke_noanswer peer is unreachable.
SIP is enabled on vpn/firewall encryption

What gives? Any suggestions would be appreciated.

Katsuodo