Disable all other settings behind NAT or factory reset your modem so that you can use DMZ. The DMZ is a conflict feature whever you have any settings for port, such as remote management, Virutal...

I checked the emulator of Archer VR400 published by TPLINK and i didn't find Access Point mode, which i found in an Archer C7 Emulator : For Archer VR400...

Sanjanna wrote Great. Thanks. It is working now. I connected the wire and logged in to console using the IP Addrss, changed the wifi details. Now I am set, room 3 has full wifi. Thank you so much....

Did you enable the IPTV on the modem? The youview box is a IPTV, isn't it? If you have enabled it, try disable it, if you didn't enable it, try enable it