SendGrid Auto-Subscribe settings page empty, component doesn't render

Just purchased the SendGrid Auto-Subscribe plugin, but I can't access the settings page for it. The "com_sendgrid" page is just blank.

Also, as soon as I add the mod_sendgrid module to any page, that page stops rendering as well. The module settings are available, though they don't include any way to configure the sendgrid account etc to use.

(Joomla 3.4.8)