I have Windows 8 on an hp laptop. I tried twice to download 4.3. I never saw any request for permission. Not sure what that means. I already donated $10. I’d like to have LibreOffice.
I get a similar error on occasion with Windows 7 and Google Chrome. Look in the downloads folder. The file may be there with a .part (or similar) extension. it will be about 215 Mb. Rename it with a .msi extension if it is there.
Try a different browser as well.
Extra thought: perhaps when the download is complete the file is scanned by an antivirus program at the same time the web browser tries renaming the file causing the error.