If you're using
netctl to manage your network connections on Arch and need to connect to a hidden wireless network, make sure that you have
Hidden=yes in your config file e.g.
Description=Your DescriptionInterface=wlp6s0Connection=wirelessIP=dhcpPriority=10Security=wpaESSID="<SSID Name>"Key="<PASSPHRASE>"Hidden=yes
netctl will refuse to connect without
Hidden=yes, even if all of the other options are correct.