Acces bloqued on USG20 for vpn L2TP

Hello, i try to configure vpn on USG following the method here
https://support.zyxel.eu/hc/fr/articles/4401915685522-USG-FLEX-ATP-VPN-Manuel-de-configuration-VPN-L2TP-sur-IPSec-mode-sur-site-

all setup is god, but :
my pc client can't connect to vpn &
on the log of vpn i see
source:192.168.1.1 to 24.0.01 acces bloqued
i don't know  what is the IP 24.0.0.1 ( my l2tp pool is 10.10.10.1 & the lan1 : 192.168.1.1)
If sommeone have an idea of my problem, 
very thanks !