Logs are not showed in WebUI

I’m using Couchbase v4.5 CE.
Currently, one of my administrated cluster are not showing log(on the webUI). I tried to solve and googled for some time but can’t find the solution or work around. So that I have to reach to log by ssh to all nodes in that cluster and find the log manually .
I wonder if anyone have ever faced the same issue before. If so please enlighten me what’s the root cause and how to solve this issue.

Thanks in advance.