@Hasayeret If you have Archer VR400 connected to the modem, check its connection settings and use same for Main Deco.

@Hasayeret 1. You will not need to do anything to define Deco mesh as running in Router mode. 2. You should have Quick Start guide with Deco set, which will guide through initial setup and...

@ZebDub88 Check this: Deco M4/S4_V2 Support Connection Preference

@Hasayeret If you have modem which is separate from the router, I would recommend connecting Main Deco directly to the modem. Main Deco in its default Router mode runs as a standard router with all...

@ErnstSl Sorry, I am out of ideas.

@TheLaughingCow You can also configure Main Network on Deco to run on 5 GHz only, to avoid WiFi interference on 2.4GHz channels between router and Deco mesh: