Please can you post your full S3 cgminer conf file? (you can exclude the pools if you want), then please can you confirm your LAN network is on 192.168.20.0?
the IP of the S3 is 192.168.20.98 as is the rest of the network is on 192.168.20.xxx
config file is below if i got it right.
config cgminer 'default'
option pool1pw '123'
option pool2pw '123'
option api_allow 'W:127.0.0.1,W:192.168.20.0/24'
option more_options '--quiet'
option pool_balance ' '
option bitmain_notempoverctrl ' '
option bitmain_nobeeper '--bitmain-nobeeper'
option freq '18:218.75:1106'
option pool1url 'stratum+tcp://sg.stratum.bitcoin.cz:3333'
option pool1user 'rippernz.antminer1'
option pool2url 'stratum+tcp://eu.stratum.bitcoin.cz:3333'
option pool2user 'rippernz.antminer1'
~
~