I have just tried with the FreeRadius server configured in ZeroShell with radtest utility.
The result is the following:
[fulvio@wks ~]$ radtest fulvio MyTestPassword 192.168.0.75 1 testsecret
Sending Access-Request of id 204 to 192.168.0.75:1812
User-Name = “fulvio”
User-Password = “MyTestPassword”
NAS-IP-Address = wks.example.com
NAS-Port = 1
rad_recv: Access-Accept packet from host 192.168.0.75:1812, id=204, length=20
and the Zeroshell log is:
12:27:04 Login OK: [fulvio] (from client server port 1)
This indicates that PAP is active because User-Password = “MyTestPassword” is a not encrypted text password.
Do you have already tried the captive portal of M0n0wall and it does not work with Zeroshell radius service?
Are you sure you configured the shared secret correctly? You have to add the IP address and the shared secret of your Monowall server in the list of the accesspoints of Zeroshell.