Unable to import presets all items were already imported

I believe those VSCO presets refer to custom camera profiles (.dcp files) that were installed by the VSCO installer.  There's a longstanding bug in LR that when you import a preset that refers to a camera profile that's not currently installed, LR silently hides that preset from display, even though it's imported:

https://feedback-readonly.photoshop.com/conversations/lightroom-classic/lightroom-classic-presets-silently-omitted-when-they-refer-to-nonexistent-creative-profiles/609d5f6ee077c600a4628cfd 

We can verify this is the issue: In the Presets panel, right-click one of the presets, do Show In Finder, open the selected .xmp file in Textedit, and copy/paste its contents here.

Normally, you'd fix this issue by re-running the VSCO installer.  I vaguely recall that it no longer runs on newer versions of Mac OS.  I think there are old discussion threads (perhaps not in this forum) about how to manually install the VSCO presets -- you'll have to google. Absent such a thread, you might look for the old VSCO .dcp camera profiles and import them into your LR by doing File > Import Develop Profiles And Presets.