This error appears in the WebSphere web server http_plugin.log. Restarting the web server should reproduce these events in the log.

ERROR: ws_os: check_file: Error accessing /path/to/plugin-key.sth. 
A component of path does not name an existing file or path is an empty string.  
Check the filename and correct the plugin-cfg.xml if necessary.

ERROR: ws_os: check_file: Error accessing /path/to/plugin-key.kdb. 
A component of path does not name an existing file or path is an empty string.  
Check the filename and correct the plugin-cfg.xml if necessary.

Examine the plugin-cfg.xml file. 

1. In the left panel of the WebSphere admin console, select Servers > Server Types > Web servers.
2. Select the web server that is producing the errors in the logs.
3. Select Plug-in properties.
4. Next to plugin-cfg.xml, select View.

The plugin-cfg.xml file will have an line representing the path to the key file (plugin-key.kdb) and stash file (plugin-key.sth).

<Property Name="Keyfile" Value="/path/to/plugin-key.kdb"/>
<Property Name="Stashfile" Value="/path/to/plugin-key.sth"/>

The errors will appear in the web server http_plugin.log if the key file or stash file do not exist on the system at the path specified in the plugin-cfg.xml file. Probably the most reasonable solution here is to use the "Copy to Web server key store directory" option to push the key file and stash file to the web server.

1. In the left panel of the WebSphere admin console, select Servers > Server Types > Web servers.
2. Select the web server that is producing the errors in the logs.
3. Select Plug-in properties.
4. Select Copy to Web server key store directory.

Then restart IHS and check the web server http_plugin.log to verify that the error's are no longer being recorded in the log file. Typically, the following events are only listed in the web server http_plugin.log after the web server is restarted.

[04/Dec/2018:22:19:19.34028] 0001408c 1b0f6740 - PLUGIN: Plugins loaded.
[04/Dec/2018:22:19:19.34033] 0001408c 1b0f6740 - PLUGIN: --------------------System Information-----------------------
[04/Dec/2018:22:19:19.34034] 0001408c 1b0f6740 - PLUGIN: Bld version: <version>
[04/Dec/2018:22:19:19.34035] 0001408c 1b0f6740 - PLUGIN: Bld date: mm dd yyyy, hh:mm:ss
[04/Dec/2018:22:19:19.34037] 0001408c 1b0f6740 - PLUGIN: Webserver: <platform>/<version> (OS)
[04/Dec/2018:22:19:19.34038] 0001408c 1b0f6740 - PLUGIN: OS : <OS> <architecture>
[04/Dec/2018:22:19:19.34038] 0001408c 1b0f6740 - PLUGIN: Hostname = <hostname>
[04/Dec/2018:22:19:19.34040] 0001408c 1b0f6740 - PLUGIN: NOFILES = hard: <int>, soft: <int>
[04/Dec/2018:22:19:19.34041] 0001408c 1b0f6740 - PLUGIN: MAX COREFILE SZ = hard: <int>, soft: <int>
[04/Dec/2018:22:19:19.34042] 0001408c 1b0f6740 - PLUGIN: DATA = hard: <int>, soft: <int>
[04/Dec/2018:22:19:19.34043] 0001408c 1b0f6740 - PLUGIN: --------------------------------------------------------------