how to ping default gateway

[aringking]

setup:
opnsense wireguard (server)
slackware wireguard road warrior (client)

slackware eth0 is connected to 4g router lan port
slackware 10.10.5.45
4g router 10.10.5.41

wireguard tunnel server 10.9.1.1
wireguard tunnel client 10.9.1.2
wireguard tunnel client wg0

on slackware client:
route table
0.0.0.0     10.10.5.41   ug   eth0
10.9.1.0    0.0.0.0      u    wg0
10.10.5.0   0.0.0.0      u    eth0

slackware rc.ip_forwarding is executable
ufw To Anywhere on eth0           ALLOW FWD   From Anywhere on wg0
ufw DEFAULT_FORWARD_POLICY="ACCEPT"

problem:
from opnsense server, can ping 10.10.5.45 (slackware client)
from slackware client, can ping 10.10.5.41 (4g router)

from opnsense server, cannot ping 10.10.5.41
is this a circular route?
is there something i miss? what is missing?

thanks.