Firewall/NAT

Hi all,
I'm new to m0n0wall.
I set up the firewall into MS-Virtual Server to realize an Hotspot with Capitave Portal
The machine is working fine.
I set up two interfaces ( LAN + WAN)
When I try to access internet from a client was have to enter a voucher id.
So far so good.
When I have to reboot firewall, it lost the connection to the Interfaces.
After it comes up, I'm not able to connect to the WebUI.
Clients are not able to access the internet. "Site not found".
Then I start the Console with Step 2 "Setup LAN IP address"
and configure the LAN IP Address.
After that, everything works fine

Is this a know issue or a failure of mine

Best regards