Not being one that uses Samsung phones, I'm going to be very limited with my contributions. However, I do see that Samsung calls their implementation "Smart View" as you indicated, and that it was working, but now isn't.
Has there been a software update to your Samsung phone? Check the settings and see if it shows when your last software update was. And if that date corresponds to the approximate time it last worked. Keep in mind that unless you use the feature often, there may be two overlapping windows in play. That is, if the update was, say, June 1, and you used the mirror feature on June 15, then it's not that update. But, if the update was June 1, and you noticed it not working on June 15, but you haven't used it since May 3rd, then it could be the update.
Check the dates, considering not just when you found it not working, but also when you actually did use it last.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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