That' s probably a issues with your VPNssl and the the settings is under your
config vpn ssl setting
And has nothing todo with a VIP per se.
btw my fwf50b does not support that cmd but this one;
fwf50b (settings) # set allow-unsafe-legacy-renegotiation
and version;
fwf50b # get system status | grep Ver
Version: FortiWiFi-50B v4.0,build0656,130211 (MR3 Patch 12)
Release Version Information: MR3 Patch 12
Also you can check if reneg is support ;
openssl s_client -connect x.x.x.x:10443 | grep Reneg
depth=1 /C=US/ST=California/L=Sunnyvale/O=Fortinet/OU=Certificate Authority/CN=support/emailAddress=support@fortinet.com
verify error:num=19:self signed certificate in certificate chain
verify return:0
Secure Renegotiation IS supported <--------