Start fresh with a factory reset.
You have mentioned "6 seconds" but actual factory reset will only triggers when you push and hold the reset button for 10 or more seconds.
Step-1: Make sure AP is getting power. Use a clip to push and hold reset button for 12 seconds. Wait for device to reboot and come online (Observe power status LED to turn flashing or stable green).
Step-2: Hookup the AP to POE injector with your laptop and assign 192.168.0.10/24 (gateway blank) IP address to your laptop. Try to ping your own IP and then APs default IP 192.168.0.1
Connect the AP to network and check what IP it gets from DHCP server. Ping the IP address.
Step-3: If you are able to ping, try to access the IP over browser and also try SSH into it with. Check if you get login prompt. Proceed further if you get access.
If still it is not working, device may be faulty and you may need to replace it.
Syamantak Omer | Community moderator | Sr.Staff TSE | CWNA | CCNA | RASZA | RICXI