I'm having the same problem, except I restored a backup that I had done prior to the Windows update, and the service isn't working on that either. Worse, I absolutely cannot uninstall Avast in any way, either through Programs and Features or with avastclear in safe mode. When I used the Account option, it told me that I had been disconnected from my account. I try to log in and it says I can't, "try again later", wtf? I think maybe it's no longer recognizing my device because I restored from a backup, I delete my device from my account on the web site, and Avast STILL won't let me connect to my account from my computer.
I tried installing Internet Security 2016 on top of what I have, and you get the spinning icon and then it just stops dead with no explanation. Same as when I try to use avastclear in safe mode. Basically any setup or uninstall program associated to Avast starts and just dies instantly with no explanation.
I can't disable the process that is running in task manager even though Avast claims it isn't running. I can't disable it in Startup processes either. This is insanely frustrating. At this point I just want to uninstall and never pay for this product again, but I can't even do that! Avast has literally become the most difficult to remove malware I've ever encountered!