School laptop is throwing a "your connection is not private" error

Ok, general update on things. 

I logged into the web interface and found where mac address access control was toggled on but was set to allow all new mac addresses (which is what I would want). Somehow my daugher's Echo and her phone (both items she hadn't mentioned had been having problems but were) were blocked. I was able to unblock her phone but despite trying twice to unblock the Echo, it remained blocked. No other devices were listed as blocked.

However, as soon as I switched off access control, the problems with her school laptop (which intermittently couldn't load most/all websites), my wife's phone, and everything else were fixed. 

I'm not sure why access control was blocking things it shouldn't or won't let me unblock her Echo but that was the problem. Being that I was allowing all mac addresses already, turning control off isn't a big deal at the moment but I hate to lose a feature.

Router is up to date on firmware and has been restarted several times since the update. It is connected to our Netgear CM1100 modem. 

I'd hate to have to reset the router and re-do my whole setup but I'm wondering if that is the reasonable next step to restore access control working properly. 

Thanks for all the help and chiming in so far. It is greatly appreciated.