Okay that's embarassing. I didn't realise there was a setting to turn WiFi scanning on. I should have read the manual huh.
Many thanks for your help though, it is working now.
One other question while you are there though - Is there a way to determine whether the RUTX11 is currently using Wifi or Cellular or WAN port for data? I have my router set to use WAN, Wifi Client, and failover to Cellular, but I need to find a way to know which mode it's currently in. My use case is that when the Wifi Client is connected, my applicaiton will upload it's data to the server, but not when on Cellular.
My reason for enabling Wifi Scanning was to maybe use the MAC address of the router to know if we're near the router. But maybe there is a better way? I can't see anything useful in the MODBUS registers for this.