Hi Chris,
I got your email as well. This error means that our plugin is unable to upload the font file in your upload folder. The upload folder our plugin uses is wp-content/uploads/useanyfont. Can you please make sure that it is permission set to create the folder and files.
Also, some security plugins are known to block folder / files creation. Can you please disable all others plugins and see if this helps ? You can later activate them once the font upload is done.
Thanks