How do you activate Generate PDF Plugin?

Please don’t laugh if this question appears silly.

I just installed and activated this Generate PDF plugin.

In settings, I selected the contact form I want to generate pdf when the form is submitted.

Then I made some changes to the settings such as Send As Attachment. then saved the settings.

I have attempted submitting several forms since then but each time I check the email, I see no attachment to the email.

Is there something I am missing?

Thank you in advance for your assistance.