DavidR
17
It isn’t Avast that should turn off Windows Defender, when you install a 3rd party AV ‘Windows’ is meant to disable Windows Defender.
There have been issues in the past if you updated windows, it disabled the 3rd party AV (not just Avast) and enabled Windows Defender. This could result in Avast seeing WD is running and enter passive mode.
That said there was also a reported issue of Avast detecting what it considered you had another AV installed (or possibly remnants), resulting in Avast entering passive mode and a problem getting it active. I believe this detection of other AVs and entering passive mode incorrectly is a bug which I believe is meant to be resolved in a later update (or possibly the current beta).