“The font may be invalid or damaged…”
This message rarely means that the font files themselves are damaged — it’s often caused by the fonts not being successfully extracted from the .zip archive you downloaded. For more information, see Opening the .zip file you’ve downloaded, and if you’re still having trouble, try re-downloading the fonts by following the link at the bottom of your receipt.
“Wait until Windows is finished using the font…”
This message may indicate that there is an administrator for your computer who has restricted users’ ability to install fonts and software.