Thanks David, I managed to get them working. I've connected them to the main unit with a cable. It allowed me then to do a reset, so they started to flash blue. Removed the cable and the app allowed...

Hi, I have the AC1200 E4R Mesh system, it was working with 4 units and then something went wrong. I've deleted the network and started from scratch. The main unit connects and 1 other unit, WIFI...