Hello oyridm

                     Online light on the modem indicates that your modem is receiving internet from the Internet service provider or not, so if that online light is OFF even after resetting you can contact your Internet service provider for reactivation of the modem to get internet back and we would also suggest you to perform proper reset once again without coax cable for 30secs, or you can follow steps mentioned on the link below to perform proper reset on the modem. If still same issue persist you can contact our phone support for warranty assistance.

                   Please visit arris.com/consumersupport for Consumer Support information.

                  http://arris.force.com/consumers/articles/General_FAQs/SBG7400AC2-Factory-Reset

Let us know if this helps.