If Google Chrome is failing to download any files, giving an insufficient permissions error, there’s a simple fix. The error is just what it says; for whatever reason, it can’t write to the download directory. Go to Settings (use the odd three horizontal lines icon on the top right to bring up a menu and click Settings). At the bottom of the page, click Show Advanced Settings. Scroll down, to find a Downloads section, and set the Download location to somewhere new – that exists and you can write to :-)
Close the settings screen and try again.
If the old download directory did exist, probably the permissions to the directory got messed up. Right click on the directory in Explorer and go to Properties / Security to fix that.
Happy Christmas everyone!