Unable to Publish forms

After installing and activating the plugin, I attempted to create a contact form from the Contact Form page. After adding and modifying the fields I wanted, I clicked Publish. Nothing happened. I also tried clicking “Save Draft”, which appeared to be working, but no drafts are visible in the Contact Form section.

Without any saved forms, when I add the widget to a sidebar and try to configure it, there are no forms to choose from.