IPv6 connection ocer PPoE

I have recently moved to a new ISP who provide me with a fixed IP IP4 address and a /56 IPv6 set of addresses.
My FTTP PPoE connection is working correctly for IP4, however I can not connect to the ISP via IPv6

I have configured my Router (TP-Link ER605) as per the ISP's instructions and the Router is sending out ICMPv6 and DHCPv6 packets but receiving nothing back.

I subsequently configured a PPoE connection on my Win10 PC cabled directly into the ONT and this connects via IP4 but again does not make an IPv6 connection.

As far as I can see using Wireshark, both the Router and the attempt via PPoe on Windows are broadcasting IPv6 packets looking for a connection but getting no reponse.

Has anyone seen anything similar, ie a PPoE connection that works for IP4 but not IPv6, and if so any ideas as to where the problem may lie, OpenReach or my ISP?

thanks

I have a different router from you (Ubiqiti EdgeRouter) but, when I was having the same issue, the 2 key items stopping me getting IPV6 into the router were specifically allowing DHCPV6 packets through the firewall and setting MSS-Clamp6 to 1432.
FWIW I never did get a Windows 10 laptop to negotiate an IPV6 PPOE connection (IPV4 worked fine) so, like you I assumed it was the ISP at fault. In my case IDNET were fantastic with their support and, whilst they didn't point me in the correct direction for the problem (my router, not supported officially by them) they did reassure me that my IPV6 profile was set up correctly.

Andy,
Thanks for your reply. My connection is now working as expected.
As usual, the problem was user error When setting up the IPv6 connection I had missed the option to use the same PPoE connection for IP6 as IPv4. So the router was trying to set up a second PPoE connection to my ISP for IP6, I blame my age!
My ISP (Aquiss) was as helpful as they could be for a router they did not support and had no experience.
I suspect my attempts to connect directly from my Win 10 PC to the ONT may have failed for the same reason but I couldn’t find any Windows configuration relating to the IPv6 connection.
Cheers