AirPort Express GEN 2 (A1392) not getting IP address

Without thinking I changed the WiFi security on my router from WPA/WAP2 to WPA2/WPA3 since I had a new device compatible with WPA3 and all others were WPA2.

The result was that 2 of my 3 AirPort Expresses no longer had internet access, and also my 3rd Gen Apple TV.

They were no longer getting an IP address via DHCP.

An issue with the AirPort Express is that resetting does not seem to clear settings.

The only solution I found was to revert WiFi security to WPA/WPA2, and then this leaves you with 2 options:

1. Change your WiFi SSID and change AirPort Express and all your other device WiFi settings accordingly, or
2. Choose manual instead of DHCP and choose an IP address outside of your routers DCHP range (e.g. my router is 192.168.1.1, the DCHP range is 100 to 199, so I set my AirPort Expresses to 192.168.1.10 and 192.168.1.20.

Note that you will need to manually enter DNS servers (e.g. 8.8.8.8, 8.8.4.4 for Google) and the subnet mask (usually 255.255.255.0).

After this they worked as they should.