Since updating to firmware version 800.0.18, my VX800V is no longer able to acquire a global IPv6 address/prefix from my ISP (Deutsche Glasfaser).

Prior to this update, IPv6 was working perfectly. My ISP uses DHCPv6 Prefix Delegation (PD) and DS-Lite. My internal network relies heavily on IPv6 for external access (VPN, Home Server), which is currently broken as the router only establishes an IPv4 (CGNAT) connection.

Technical Details & Troubleshooting performed:

1. ISP Verification: I have contacted my ISP (Deutsche Glasfaser) support. They have confirmed that the DHCPv6 "Solicit" message is received from my router and a valid IPv6 prefix is successfully assigned/offered to the device. However, the VX800V does not seem to bind or apply the assigned address to the WAN interface.

2. Configuration: The WAN settings are configured for "Dynamic IP" with IPv6 enabled (DHCPv6/SLAAC). Prefix Delegation is active.

3. Reboot/Reset: I have performed multiple restarts and a factory reset of the VX800V, but the issue persists on version 800.0.18.

4. Impact: Without a Global Unicast Address (GUA), all inbound IPv6 traffic is blocked, making remote access to my local infrastructure impossible.

Requested Action: Please investigate if there is a regression in the DHCPv6 client stack of firmware 800.0.18 specifically regarding ISP handshakes for DS-Lite/GPON connections.

• Is there a beta firmware available to address this?

• Are there specific advanced settings (e.g., DHCPv6 Option 16/17 or Rapid Commit) that need adjustment for this specific firmware version?

I am looking forward to your technical feedback.