AC1900 WiFi cable modem not connecting to upstream channels

[dhaider]

Has anyone had the experience that the upstream light will start blinking after about 5 minutes of resetting?  I understand that this means the modem is not locking onto a upstream channel.   When checking the modem setting via the genie app it shows that all 4 channels are locked.

[FURRYe38]

Which CM or C series modem do you have? 

Have the ISP check the signal and line quality UP to the modem. 
Be sure there are not coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem.