I believe I've found a workaround for this error:
Simply put, if I am not already connected at system boot, and already am finding this error, it will persist even with multiple reboots.
Solution: Connect the system (CAT5 cable) before a cold boot and boot. Seems avast checks and registers the system early in the boot process for Secure DNS, and will only work if this is done this way. Any other way is potluck, may work, may not. Have not checked to see if this works if an automatic wireless connection is made at logon, but suspect this may work also.
No need to be connected after any subsequent start-ups, you can leave the system disconnected if you like.