Hey, I just spoke to a Samsung rep. If you go into your settings and rest all the settings (not the entire phone), it might work. It worked for me. Just remember to add the wifi back before doing it. Hope this helps.
Alright...so I have the same issue others are having but I am hoping this will give some good information to the folks at Samsung to help narrow down why this is happening. I have 3 Samsung TV's all equipped with screen mirroring. My main tv in the living room was new at the end of 2016 and the ones in my bar in the basement are a 3-4 years older. My note 5 always worked like a charm on all 3 tv's. My note 8 started out working fine all on 3 tv's and it still works on my newest tv just fine. That said the 2 in my bar it either wont connect at all or if I am lucky enough to connect it only stays connected for a minute or less and has been doing this for many months. The last 2 updates have not helped fix it either. I have cleared my cache restarted it prior to connecting. I have also played with turning the phone visibility on and off with no change. Its very frustrating as the 2 in my bar are where I use it most to play music when people are over so now I am without. Samsung...I hope you see this and are working on a solution. This feature was a big selling point for me!
I think I may have found a fix for some people. Basically mine was working for the most part and stopped working last week. I noticed I had installed an Adblocker app and after I uninstalled it, smart view connected right away.