If the online light is solid you can try resetting modem and check the internet connection and if there is no internet to make sure whether the modem is getting internet from your Internet service provider or not please login to your ISP application to check the modem is online or offline and if you see the modem is offline on the ISP application you can try self activation or contact your ISP to reactivate modem. Please follow the steps mentioned on the below article to perform hard reset on the modem.

http://arris.force.com/consumers/articles/General_FAQs/SBG7600AC2-Factory-Reset