@gabyavra May I know who is your ISP? What is the WAN IP address on the C80? What is the error message when you are trying to connect to the L2TP VPN server? How about referring to this...

@Kenny2021 There is no whitelist for Access Control when the C80 is working at AP mode. If you do need the whitelist feature, please change it to router mode.

@kromozome Have you tried to disable the NAT boost on the C6 as suggested previously? BTW, how much download and upload speed you can get when connected to the C6 network? What is that provided by...

@jimas That is one of the WAN connection types provided by the Internet Server Providers mostly in Russian, it is not commonly used for connecting to a normal VPN server, which could be encrypted....

@nibras Hi, you can contact the support team via email here: https://www.tp-link.com/support/contact-technical-support/#E-mail-Support

@Kalle If that is the case, we recommend reaching out to the local tech support, so they can work with you in looking into the issue further or help with the replacement.