When I deactivate the plugin, I’m able to edit my blog title font and it stays changed, but then if I go back to activate the plugin, the blog title font changes back to the old one I don’t want to use anymore. The only solution I see is deleting this plugin and finding a new one.
Sorry about the issue you are going through. Since you have already deactivate the plugin and am unable to check further. If you wish and can enable it and send me your site url, i will check it here and try to find out the cause.