There is a problem with the latest update, the GUI keeps displaying " You are unprotected" , try icon show error, Settings cannot be saved, Licence information not shown, database version not shown , context menu scan object not working … and many more things tha dont work.
But the services are running because i testet the antivirus using some malware files and EICAR file and it detect them.
https://s32.postimg.org/gafmnpw35/abt.png
https://s32.postimg.org/8j3i2whbl/activ.png
Yea same problems here. The update is more of a malware than a fix. :
>:( >:( >:(
The NITRO update is BROKEN even without fighting any malware 
Having same issue. After updating all shields break and can not be started. Keeps saying something is turning off background services. Even after telling it no, still shuts them down. Additionally, used AvastClear to remove all traces, did a clean install. Scanned the system while it was working but after reboot, did the same exact thing, all shields went down.
Scan came out negative for anything. Even for giggles had a full scan with Panda just to make sure and same, nothing found.
Points to a definite break in the engine.
I am having the same problem, downloaded new update, restarted computer, now Avast is telling me I’m completely unprotected, tells me the service is turned off, and when I click resolve all, it says a program is trying to shut it down, and doesn’t do anything else.
Follow instructions: https://www.avast.com/faq.php?article=AVKB33#artTitle
Problem already fixed - https://forum.avast.com/index.php?topic=189131.msg1328660#msg1328660