its because you’re accessing it with a local lan address and not a https address. (you’ll get the same notice if you try using a http address) 

For years I have used the standard ARRIS address of 192.168.0.1 with no https or http. A post told me how to adjust the Firefox security settings and I can again log on to my Surfboard information site at 192.168.0.1. He said Opera would work with that address. I don’t know if there is a fix for Edge or Chrome.  

Here is an image of the Firefox fix noted above.