quick and short update:
it's because
https://www.litespeedtech.com/suppo...n_installation:advanced#cache_policy_settings
strictly follow the wiki to fill server level "Storage Path" with "/cache/storage/path", but not crate the path manually.
another issue found:
in above wiki, regarding cache policy:
"As our default settings work well with most caching scenarios, it is not common to have to change any of these settings."
per the screenshot, all is "Not Set"
while in lscwp(lscache plugin for wordpress, now version 1.0.7.1):
LiteSpeed Cache -> Information -> Configurations:
The following are also recommended to be set:
Cache Request with Query String - Yes
Cache Request with Cookie - Yes
Cache Response with Cookie - Yes
Ignore Request Cache-Control - Yes
Ignore Response Cache-Control - Yes