@Lucas_Andrade 

The same issue. Clients don`t receive ipv6 address. I was talking to my ISP, and we fixed some problems on their side, and it works perfectly in ND Proxy mode, but not in DHCPv6. I`ve enclosed a screenshot.

  @Asic 

Hi, I solved my problem, but i thing the problems are different.

My problem happens when i try to receive de IPV6 from PPPoE connection, you are trying to receive the IPV6 by Dinamic (DHCPv6) on WAN port.

ND PRoxy works when your modem/router befor you tplink make the connection/authentication with ISP. in this case, the ND Proxy works like a bridge into your tplink and you ISP modem/router.

How are you config's for IPv4 Connection? are the Dynamic to or PPPoE?

Your ISP modem is configured to Bridge or Router mode?

Some ISP need to authenticate PPPoE IPv4 and IPV6 separately. For this you can unselect the 'Share the IPv4 PPPoE connection/Authentication' on IPv6 configuration. This solve my case.

i Think the you tplink is configured like like a router after another router (ISP), and this is not right. the NAT configuration doesnt works in this case.

Yout need to put your ISP modem/router in bridge mode and make the authentication with the TP-link, 

OR you continue with the ISP modem/Router in the router mode and put your tplink in bridge mode.

  @Lucas_Andrade 

Hi! Thanks for the reply.

My ipv4 Internet Connection Type - Dynamic IP or I can use Static IP (the same IPv4 I get in both cases). My device works in Wireless Router Mode.

I`ve tried to change device mode to bridge and I lost my internet connection at all. Probably, it doesn`t work in my case.

  @Asic ,

If you already configure a static IP on IPv4 Interface, you dont use PPPoE.

You need do setup the IPv6 like IPv4, like Dynamic(Slaac/DHCPv6).

If your IPv4 is fixed, probably your IPv6 can fixed too. 

You need to talk with your ISP to configure.