Can't see a subnet behind OpenVPN client

[d3bian]

Hi, I have this working OpenVPN setup running on OpenWRT routers:

LAN (192.168.2.0/24) HOSTS
|
ROUTER 192.168.2.1 (OpenWRT, running OpenVPN SERVER)
|
MODEM VDSL 192.168.1.1
|
----- INTERNET
|
MODEM 4G/LTE 192.168.8.1
|
ROUTER 192.168.3.1 ((OpenWRT, running OpenVPN CLIENT)
|
LAN (192.168.3.0/24) HOSTS

The VPN works well and I am able to connect from hosts on OpenVPN server side to hosts on OpenVPN client side (and vice-versa). Furthermore, I am able to connect to 192.168.1.1 (the VDSL modem) from hosts located in the 192.168.3.0 LAN.

I am hardly trying to connect from hosts located in the 192.168.2.0 LAN to the MODEM 4G/LTE (192.168.8.1), I made many attempts but without success. Hereby my configuration files:

======================== /etc/openvpn/server.conf =====================
======================== (on OpenVPN server router) ====================
dev tun
proto udp
port ******
ca /etc/openvpn/ca.crt
cert /etc/openvpn/server.crt
key /etc/openvpn/server.key
dh /etc/openvpn/dh2048.pem
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "route 192.168.2.0 255.255.255.0"
push "route 192.168.3.0 255.255.255.0"
client-config-dir ccd
route 192.168.3.0 255.255.255.0
route 192.168.8.0 255.255.255.0
client-to-client
keepalive 10 120
tls-auth /etc/openvpn/tls-auth.key 0
cipher AES-256-CBC
status openvpn-status.log
log openvpn.log
verb 3
explicit-exit-notify 1

======================== /etc/openvpn/ccd/client1 =====================
======================== (on OpenVPN server router) ====================
iroute 192.168.3.0 255.255.255.0
iroute 192.168.8.0 255.255.255.0

======================== /etc/openvpn/client1.conf =====================
======================== (on OpenVPN client router) ====================
client
dev tun
proto udp
remote ****** *****
ca /etc/openvpn/ca.crt
cert /etc/openvpn/client1.crt
key /etc/openvpn/client1.key
remote-cert-tls server
tls-auth /etc/openvpn/tls-auth.key 1
cipher AES-256-CBC
status openvpn-status.log
log openvpn.log
verb 3