Mac or Windows? What version?
What exact version of Lightroom are you using (x.y.z)?
What URL are you using for the download?
What exact error message are you getting?
I am using a Mac running El Capitan.
I am using LR 6.4
I went to this URL: https://creative.adobe.com/addons?pp=PSLR
I tried to download the free Wintry Wonderland set of presets. It appears to download but does not. When I go back and click on the Wintry Wonderland preset I am taken to a page that says it was Acquired. "Where to find it" says it is in my downloads folder but it is not.
The preset description is as follows:
DescriptionFrom black & white, desaturated, and dehaze presets, all the way to sky enhancers, vintage retro, and other various looks to help you achieve the perfect winter look for your photos!
The presets included in this set are compatible with Adobe Lightroom 4, 5, 6, and CC and will work with RAW as well as JPG photos (we highly recommend shooting in RAW).
I can confirm that the plug-in does NOT download even though the CC app thinks it is syncing something.
Certainly the plug-in does not get installed.
Most likely this will require someone from Adobe getting involved, most likely not in this user-to-user forum.