I have 3 existing Deco x20 devices connected & working correctly. The 2 secondary units are wired in series & if disconnected the revert to wireless but still work correctly. I'm trying to add another Deco x20. The app fines it,adds it & it turns green. But when check on the app it says ite offline. I have tried it wirelessly & by adding it to the others via an Ethernet cable with the same result.