How to make IPv6 work on Almalinux

Hello. I am working on setting up a home server with almalinux. The server is under a firewall with IPv4 connection as PPPoE and IPv6 as DHCP6 based on IPv4 connection. On a Windows computer, IPv6 has internet and is completely normal to use. On Almalinux the system still receives IPv6 but no internet.

[root@local ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:f4:33:0e brd ff:ff:ff:ff:ff:ff
    inet brd scope global noprefixroute ens192
       valid_lft forever preferred_lft forever
    inet6 2402:800:63bb:99e4::100b/128 scope global dynamic noprefixroute
       valid_lft 86362sec preferred_lft 86362sec
    inet6 2402:800:63bb:8996:20c:29ff:fef4:330e/64 scope global dynamic noprefixroute
       valid_lft 86397sec preferred_lft 14397sec
    inet6 fe80::20c:29ff:fef4:330e/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

[root@local ~]# ping
PING (2404:6800:4003:c04::71)) 56 data bytes
--- ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3100ms

IPv6 mode in almalinux I’m setting to Automatic. IPv4 is Static. I’m researching and trying some solutions but it doesn’t work.

Thanks @minhvip. Can you please post your config from /etc/sysconfig/network-scripts/ifcfg-ens192 to start? Let’s take a look there first.

Also, what do you get with:
ip -6 ro

The nmcli can show the stored configuration of connection (if NetworkManager.service is in use, which is the default):
nmcli -f ipv6 c s ens192
(That assumes that name of connection is “ens192”. nmcli c s lists connections.)

Furthermore, the current active config can be seen with:
nmcli -f IP6 c s ens192