RV50 to Fortigate IPSEC VPN

I need to connect some PLC using RV50 via 4G, dynamic IP, through IPSEC VPN to a central Fortigate Firewall.

I’m facing two issues:
1 - no routing between lans, from the Fortigate side I can only ping the RV50 private lan interface, what I define as gateway address for my PLCs. Nothing else inside the network and no errors in logs.
2 - Dropping the VPN via Fortigate takes really a LOT (hours) to come up again without a reboot. Am I missing something?

Is there a configuration guide or raccomandation for these routers?

Thank you in advance.