A few days ago, all sharpening starting becoming lost when I go from Develop to Library mode. The Library view is the same as when I move the sharpening slider to 0% in Develop mode. This loss occurs at 1:1 and all other viewing sizes too. The sharpening loss occurs when I export too, even at the highest resolution. I've used Lightroom for several months and this issue didn't start until a few days ago. I'm using version 5.7. Thanks for your help.
Sharpening in the Develop module can look overdone or sometimes less-sharp at Fit zoom (as your screenshots apparently are) because of the inaccurate resampling algorithm for fast screen display so Develop can look either much more or much less sharp than Library and Exported photos.
However, that doesn’t explain why you’re seeing a difference only recently.
The most useful screenshots to prove the sharpening slider isn’t working would be ones at 1:1 or maybe 2:1 (2x zoom) of an area that should sharpen up reasonably well like the twigs and it would be preferable to see the actual Detail section settings alongside in the Develop view.
It would also help to have access to the original raw file to download to compare how things work on our systems as opposed to yours. To share a raw file, upload one to www.dropbox.com <http://www.dropbox.com> (or skydrive or google drive or idrive or wherever allows public sharing) and post a public share link to a reply, here.