Hi Lee,
I am a user who had the same problem but fixed it. The instructions in the documentation are clear but i overlooked them. What you need to do is this:
- Make sure "memory_limit" parameter for PHP is set to a value higher than 50MB or more. Not a value of -1 (this was my mistake)
- Upload only one .ttf font into Font Squirrel and generate the font. Although Font Squirrel can take more .ttf files in one go, SPPB can only process one .ttf in one upload file. (This was another mistake i made)
- Download the zip file from Font Squirrel and upload the zip file Font Squirrel generated to the Font Book.
Then you should see the font list under the "Installed Font". Try it.