Since you are having flashing online light on the modem you can try performing hard reset on the modem then check for LED light status and also please check for the LAN and WAN IP address mentioned on the modem GUI or interface.

To reset modem  please, disconnect the coaxial cable from the back of the device? At the back of the modem, in the middle section you will see a small hole, inside that hole there is a button, and that is the reset button, please insert a paper clip or a tip of a pen and hold it for 15-30 seconds until all your lights go off, afterwards connect the coax cable back and wait until your device fully boots up.

To check IP address login to the modem GUI

Launch a web browser, such as Internet Explorer, Firefox, or Safari.  Enter http://192.168.0.1 into the address box, and press the Enter key.  The https:// Redirect page will appear.   
Enter admin in the Username field and enter the custom password in the Password field.

Click the Login button.  The Gateway > Summary page will appear.

Select  Gateway > Connection > Status

you can see WAN IP address and IPV4 which is the LAN IP.