I have a paid Avast Internet Security, on Windows 10 Pro, 64-bit., and it has happened to me also. It also happened on two other computers that I have worked on in the last couple days. One was Win10 Home and other was Win 7. I am patiently waiting for Avast to fix this problem for my computer, but on computers I am working on in my business, I will have to install something other than Avast (free or paid). I put Avira on the Win 7 computer. I can't let a computer go back to customer with an error showing on the antivirus program, they wouldn't stand for it. I hope this gets fixed...FAST. I have been using Avast Internet Security on my pc for about 5 years, this is the most trouble I have ever had with this program. I have put Free Avast on hundreds of computers, now they are calling me to fix this problem.
On another note, about 3 or 4 weeks ago, I have no longer been able to save the Avast Configuration file to any computer.