Hi, i'm new here, I had the same problem but I find a solution, when you stop the sslstrip you need to clean the iptables with these comands by ssh terminal
iptables --flush # there are probably too many resets here,
iptables --table nat --flush # but at least we're sure everything's clean
iptables --delete-chain
iptables --table nat --delete-chain.
I hope this can help you, sorry for my bad english