If you are on windows you can force windows to use IPv4 for your netconnection somewhere in the network settings given your provider and router supports IPv4 and IPv6. But this is only required if you plan to host a masternode because Masternodes work with IPv4 only. I would not recommend it.
I'm pretty sure I saw a couple of masternodes on the list with ipv6 at some point. But it might have been another coin.
Is the ipv6 not working a bitsend thing only or for masternodes in general?