Did Marshmallow disallow SMS sync apps from remotely clearing notifications?

[AC Question]

Hi! I just upgraded from a Note 2 to a Note 5, which bumped me up a couple of OS versions. I have been using mySMS for a while -- it lets me send texts from my PC, and *used to* sync notifications (when I read a new incoming text in the web app, it would clear the notification on my phone too).

Now however, it seems that the notifications on the phone don't clear. I have done the recommended steps (set mySMS as my default messaging app, etc.). I have also googled this issue and found a few other people with the same problem recently, but no solutions. Does anyone here know what might be up?

Thanks!