Likely your form does not have a submit button or the form submit event is not triggered in your website. To record a form submit manually, call a method _paq.push(['FormAnalytics::trackFormSubmit', formOrFieldElement]); whenever your form is being submitted. formOrFieldElement can be either the form element itself or any element within your form.

Previous FAQ: How do I stop the tracking of a form that Matomo has created automatically?