If you're a Directory member and don't pay your subscription, your profile will be 'archived' and you won't be able to update it. You also won't be contactable through the site. As soon as you resubscribe, your Directory membership will be restored.
If you're signed up to Opportunity Finder membership you'll lose access to the Opportunities section of the site.
If you're a Network Associate you'll lose the benefits of that membership which includes insurance cover.