I have purchased some zip presets. When I go to the edit section and it preset then go to the three dots at the top, it should have upload presets. It doesn't. It states "Hide Partially compatible presets". I am not able to upload the zip files.
Have you tried importing via the File Menu / Import Profiles and Presets?
Also, is Hide Partially compatible presets ticked? If so, try unticking.
Apart from that, all I can think of is do you have any Preset Groups hidden in Manage Presets, especially User Presets?
And finally, what format are the files within the zip? If they are XMP they should import. If they are DNG, then this file would need importing as a photo and you would need to Create Preset from the settings applied.