Arris units are malfunctioning. I assume you have Xfinity? Four months ago, they posted about this and said “we are working on it” with no update. I just posted yesterday about this with 0 response. But if you look around the posts, we are all having this issue. Xfinity is no longer compatible with Arris. It keeps restarting. If you bought recently, return! If, like me, you’ve had it a couple years, I would contact Xfinity and ask them about it. They will blame Arris. Arris blames Xfinitity for failing to update firmware. 

Its supposed to blink. 

Here’s the led faq

https://arris.my.salesforce-sites.com/consumers/articles/General_FAQs/SBG8300-LED-Light-Status/?l=en_US&fs=RelatedArticle