I suggest you can try to use wireless router modem, and use EWAN port to connect your VR600 to fiber modem by cable.

If you want change the operation mode, you can change it from Advanced->operation mode in admin page. 

VR 600 operates in three modes: 3/4G router、wireless router and DSL routing.

About your EWAN port, you can check the LAN port of your router, you will find the EWAN/LAN port.

Hi, done all of the above, but no internet connection.

You can also try to give a call to TP-Link customer service department.

 https://www.tp-link.com/en/contact.html

@Larry47 Did you get this to work? I am currently having the same issue now where the Archer VR600 i not letting me connect to the web management console and when I set it up through the tp link app; it tells me no internet connection