Only Archer C9 V4 and V5 support open VPN and PPTP VPN.

802.11lk&v needs clients to support, but normally most recent devices already support this protocol.

Did you reset all three plugs by pressing the wifi settings button for 10 seconds? Only reset and reconfiguration will make the plugs work with the new router. Remember to enable remote control .

It seems to a compatible issue. Have a try to upgrade the router's version?

It only support client to server PPTP VPN which only allows PC or phone to connect.

My bad, didn't notice your location. You can contact support.usa@tp-link.com and ask TP-Link support for a firmware for us. If your TL-WR902AC is not on repeater mode, then it is not affected.