Netgear N600 cable modem router model C3700

N600 is acting strange today (this morning), my PC was not able to connect to yhr router, after power off and on, power led light on, a few seconds later, the next 3 led lights flash 6 times simultaneously, then all led lights on once, then all off except the power led light, wait a few seconds, the next 3 led lights flash 6 times simultaneously again, then all led lights on and off again, appearing it was forming a boot failure cycle, trying to, but can't, boot, again and again.

What does the 3 led lights (down stream, up stream, and Internet) flash 6 times mean? (trying to tell me something?)

Thanks for your help!