Device connection failure

When adding a Zigbee sub-device, the message "Unauthorized, unable to add" appears, and the gateway cannot find the device. What should I do?

How to troubleshoot if Wi-Fi device fails to connect successfully?

Why the device failed to connect (Bluetooth)?

What should I do when my device fails to connect to the network?

How do I check whether the router's password is incorrect?

Do I have to reconnect all my devices to the network after I change the Wi-Fi password?

How do I choose between 2.4 GHz or 5 GHz networks for my device?

（NETGEAR Router） How to configure the router as a DHCP server?

Why the device failed to connect (Zigbee)?

How do I troubleshoot a network pairing failure caused by an incorrect router password?