The original post is describing that nothing done in Develop is seen in Library, not necessarily what you’re describing of sharpening isn’t seen in Library and Export, so it may or may not be the same thing, and probably not.
If it is a problem with Library, perhaps the Previews cache is corrupted since that is where Library gets its images to display whereas Develop computes things in memory.
The way to fix corrupted previews is to remove the entire previews folder. You do this by locating your LR catalog in Windows Explorer or Finder, then looking for an FOLDER (not a file) with the name of catalogname Previews.lrdata, and delete that .lrdata folder. You need to be out of LR when you delete it.