I have set up a Raspberry Pi 4 without a monitor using this guide, but it wasn’t connecting to my wifi. When I connected it with ethernet and ssh’d into into it I saw this message on boot: “Wi-Fi is currently blocked by rfkill.”.
Apparently, rfkill is a “tool for enabling and disabling wireless devices”. Calling it with the rfkill command shows you if your Bluetooth or Wifi is disabled. Then you can type this to enable them all:
rfkill unblock all