Hi wallabybob,
you are right. Changing the dns rule didn´t will fix the problem. Today, i have checked the problem with one of our device. If i didn´t enter a voucher ticket and try to catch mail or do other communication to the internet, so transfer will blocked. If i will go to a www url over port 80, the captive portal catch me and ask me for a voucher. Looks all ok. Only the firewall log makes me crazy.