Cannot find imported presets (Windows 10)

I have often uploaded presets that I purchased as XMP files in to Lightroom, via different methods (dragging them into the presets list, importing them via Import Profiles and Presets), but now I just cannot find the latest sets of presets.  I searched high and low everywhere in Lr, also enabled Show Partially Compatible Presets, but nothing ...  I tried to import them again several times, but get a notification that the files have already been imported.  

Where can I find these presets?  I even asked the seller what he named the files, in case they're called something different, but they should be easy to find in my presets list ...

Help please!