My catalog shows 2k+ images labelled "Photos That Failed To Build a Smart Preview" however when I create Smart Previews of these images they do not get removed from this set nor does the quantity of photos decline.
Screen grab shows an example. Any suggestions for a fix are welcome.
LR sometimes soils its preferences file, and resetting it can fix all sorts of wonky behavior. That article explains how to restore the old preferences if resetting doesn't help.
2. Use the free trial of the Any Filter plugin to see what the catalog internally reports for the presence of the smart previews. Select the built-in collection Photos That Failed To Build A Smart Preview, run the Any Filter > Filter command, click the magnifying glass, and select the Has Smart Preview criterion:
If Any Filter reports that all those photos in fact have smart previews, then the problem is just that the built-in collection isn't getting updated. But if Any Filter reports that those photos don't have smart previews, then the problem is more serious.
I have never seen this message, but it looks to me like the smart previews are corrupted. Lightroom can simply rebuild them: Move the <catalog> smart previews.lrdata out of your catalog folder, start Lightroom and try buidling some new smart previews. If that works without a problem, then that was probably it so you can trash the old smart previews and build new ones for all your images.
p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post if it helps you get responses.