Symptoms

CT is configured with routed IPv6 address. Node is pingable while CT does not response. 

Cause

checked the configuration for IPv6, and observed that forwarding  was enabled for interface br0, while IPv6 address is configured for br1. I manually changed this option, after that CT became avail from Internet.
 

[root@vz790 ~]# cat /proc/sys/net/ipv6/conf/br0/forwarding
1
[root@vz790 ~]# cat /proc/sys/net/ipv6/conf/br1/forwarding
0
[root@vz790 ~]# echo 1  /proc/sys/net/ipv6/conf/br1/forwarding

Solution

To make this option permanent please add to /etc/sysctl.conf:

net.ipv6.conf.all.forwarding=1