@Mjack You should set this in Virtual Servers. The reason for the error message is that you are trying to set an IP address within different subnet. For example if your router LAN IP address is...

@Shxy6 With the TP-Link RE you're extending your main wireless network, so you do have a main wireless modem/router. Thus the DNS setting should be done in your main wireless modem/router. Although...

@Olufowobi To be able to access the Internet you should use an ethernet cable between the Fiberone Modem LAN port and the WAN port of your WR940N. If you already have cable plugged, then replace it...

@Shxy6 Uninstall the Deco app since you don't need it - it was just an example what should you do to resolve the issue with the warning message. That could happen with iOS devices wheather they are...

@pawelgrzybek Have you tried to set the IPv6 address in its expanded format: fd65:a96f:f7e2:4166:e443:007e:0fa9:f46c or if that doesn't make any difference to include the routing prefix:...

@Olufowobi How do you receive your Internet service - any ISP modem/router before your WR940N or ISP ethernet cable direcly to the WL940N ? What's your router status showing here: