You can close the form to stop accepting responses. When you close your form in Neartail, users will not be able to view the form or submit their response, but you can edit the form and manage responses. Login to Neartail > click on the form to open it > Edit page will be displayed > In the Neartail Edit page, click on the gear icon next to the form title > Form settings will be displayed > click Advanced > check Close this form option, add a custom message and click Save.

its not showing up on my forms list

You can close your form in Google Forms. Open your form in Google Forms > click Responses > disable Accepting responses option, add a custom close message > click on the addon icon > click Neartail > click More options > click Update to sync the changes with Neartail. If you close your from in Google Forms, you will not be able to edit the form and manage responses using Neartail.