Does UrBackup offer ipv6 support?

I’m disabled all IPv6 options on my OpenWRT router for LAN,
make static IPv4 lease for that mac, so client received ipv4 address,
but UrB server can not add that client in active list,
only in “hints for discovery” section, and “offline” after some minutes.
Client is win10, sw installed by admin, all defaults.
What’s goes wrong?
Some ports should I allow manually? (setup always do it, but failed?)
Should I reinstall it now, where is IPv6 environment is disabled now
and so client will not try to bind to UrB by v6 again?