I have about 200 computers at work. I started task to update program from 19.5 to 19.6. Why on Earth is this update so slow? It take several hours on each computer, usually two or three, but my record is 6,5 hours! Frankly speaking it’s faster to uninstall and reinstall whole Avast. 
When I try perform update manually it is searching for update for hour or two on this screen.
Sometimes after finally finding and installing update it displayed this. You really don’t wanna see that after waiting almost three hours!
I apologize for your update issue. Please create a case at https://www.avast.com/business-support-contact