Christopher, when you notice that the notifications have stopped in the web interface, can you open the developer tools and look in the console.  There should be text in there about SignalR connections and a self-test it runs to try reconnecting.  Does that self-test pass or fail?

Robert, will check here in a day or so when I notice ActiveSync notifications being delayed heavily.

I also setup an automated nightly pool recycle for the SM app pool. Previously this did not exist, this may help, we've used it in the past, but caused complaints from clients when the pool would recycle.

Even 6956 build , not giving notification in google chrome( Version 71.0.3578.98 (Official Build) (64-bit)) ,  I have followed few link from smartermail forum

  In  user settings  still show "Browser notifications have been disabled in this browser"

Let me know how to resolve the issue ?