Diagnosis
A firmware update can reset or change the 2.4GHz broadcast settings, particularly the channel width or security protocol, which many IoT devices are hypersensitive to.
How to Fix It
Log into the web interface (orbilogin.com). Go to Advanced > Setup > Wireless Setup. For the 2.4GHz network, set Channel Width to 20 MHz only, and set Security to WPA2-PSK [AES] (not WPA3 or WPA2/WPA3 mixed). Save, reboot, then try reconnecting your devices.
If That Didn't Work
Some devices need the 2.4GHz network to have a completely separate name (SSID). Create a dedicated 2.4GHz guest network with a simple name/password and connect your IoT devices to that.
Heads Up
Many smart devices can only connect during a short window after being powered on. After changing settings, power-cycle the smart device immediately before trying to connect.