If the modem is not getting internet and you see IPV4 error you need to re activate modem by the on your Internet service provider application or by contacting ISP for activation to get internet back. If even after activation there is no internet you can perform hard reset on the modem by following the steps mentioned on the below article.

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Factory-Reset