1. Did you create the group on your account before you created your webform?
2. During the process of creating your webform did you make the link with your pre-created group within Step 8, by selecting that group from the drop-down menu before you saved your webform?
3. Have you checked that your web sign ups are coming in as individual contacts?
3. Have you tested the process by signing up yourself with a fresh valid email address?
If you have actioned the above and still have problems, please raise a support ticket to us and include all the relevant details. We can then look into your situation and advise you.