Wifi device connected in logs but not in client list. Connection refused.

[Thomasx]

Hi

I have some connection issues with a WiFi device. The device reports it is connected to WiFi.
When I look in my router RT-AC87U the device is not in the client list, indicating it is not connected.
However, when I look in the System Wireless Log, the device is there with the IP-adress it last connected with and it says it's been connected for an hour, which is correct as I restarted it a an hour ago.
The flags in the log says PSTAU_

What could be the cause, when the logs says the device is connected, but the client list does not show the device?
And at the same time, the device says it is connected, but when it tries to communicate, it reports "connection refused".

If I try to ping the device, I get Destination host unreachable.

It's the device at the bottom of the list below.

Thanks!