If a device, that has already been assigned an IP address and listed in the Devices list, receives a new IP assignment and gets placed in the "Unsorted devices" group on a new connection, most likely, it changes its MAC address for each connection automatically. Mobile devices are most susceptible to this.
MAC is a unique identifier that is not changed under normal circumstances. However, starting from Android 10 and iOS 14, both operating systems include a default setting to randomize its MAC address every time it connects to a network, even if it's a known network.
So, if that is the case, it is necessary to disable MAC address spoofing.
Here is how to do that in iOS:
Open the Settings app and connect to a Wi-Fi network.
Tap the "i" icon on the right side of the Wi-Fi network name.
Toggle Private Address to Off.
Return to Wi-Fi Settings and turn Wi-Fi off and back on again
Here are the steps for Android:
Open the Settings app
Select Network and Internet (or Wi-Fi & internet)
Connect to the wireless network
Tap the gear icon next to the current connection
Select "Use device MAC"