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Did you replace the cursor files in the right directory? They don't belong in your downloads folder.
Those would be in C://Program Files/EA Games/The Sims 2/TSData/Res/UI/Cursors or .../Origin Games/The Sims 2 Ultimate Collection/Base Game/TSData/Res/UI/Cursors
The ZIP-file for Clean UI should contain an installation instruction as well
The dev said that you need all the EPs and all other packs for the clean UI to show up. I have the UC so everything went fine even though it took a long time to set up. Perhaps there are missing files related to not having the EPs and SPs where the clean UI needed to function normally.