Can't install new fonts in Windows 10

I am using Windows 10. Every time I try to install a font I get the below message.

The file does not appear to be a valid font

• I have gotten files from many different sites.
• I have tried both .ttf and .otf fonts.
• I have checked my firewall. It is on. My machine won’t let me turn it off anyway.
• I have given myself administrator permissions.
• I have changed the file ownership on the file.
• I have tried a scan of the machine.
• I have tried several file converters.
• I have tried making a copy of the file and installing the copy.

How do I get this to work?

tl;dr: You need administrator privilege and (probably) install this font for all users -- at least this is the only way that I found working on my side.

Double-clicking on a .ttf file ends with:

Right-clicking on .ttf file and selecting Install ends with:

Right-clicking on .ttf file and selecting Install for all users:

does the magic!