Fixlets may be relevant on a computer.
Computers may be applicable to a fixlet.
Those should show the same relationship. An Action that results in Not Applicable, is usually because the client has not recently reported on the fixlet.
You can use the Fixlet Debugger, or the WebUI Query app, to test the relevance on the end computers and determine where the issue occurs.
Otherwise we’d need to do look at the specific details on what you’re seeing.