Ap Offline Issue

Our 2 of the 3 AP's became offline at 22.06.2019 around 11:00 GMT+3. They didn't turn online until i unplug and plug cables when around 20:00 GMT+3
I can't find any reason for that. Is there any option for find logs or root cause? I don't want any internet outage in our office so i have to figure out reason and prevent same situation.
Our AP's x-1
Firm version: 2.2.0.0.45
Comments
Hello one of my AP gone offline again.
Could you help me about that?
Hi @webadmin,
Can you please share the serial number of the AP to [email protected] ?
Thanks
Ramesh