Google Forms has implemented a new update that requires form owners to publish the form to collect responses. If the form is not published, you will not be able to add signatures using the Formesign addon. Open your form in google forms > click on the Publish button in the top right corner > Publish form settings popup will be displayed > click Publish. Once the form is published, you can click on the addon icon > click Formesign - eSignature > click Configure e-signature menu option > enable signature and click Next > click Preview to test the form or click Proceed to open the Formesign Editor and customize the form.