Cloud Hosting

If you are using older versions of Avast or AVG Antivirus, Microsoft has placed a compatibility hold that will prevent you from upgrading to Windows 10 1903 or Windows 10 1909 until you upgrade to a newer version of the antivirus software.

In a support notice to the Windows 10 Health Dashboard for Windows 10 1903 and 1909, Microsoft has stated that users who have AVG or Avast Antivirus versions 19.5.4444.567 or lower installedwill be prevented form installing the May 2019 Update and the November 2019 Update.

"Microsoft and Avast has identified compatibility issues with some versions of Avast Antivirus and AVG Antivirus. Any application from Avast or AVG that contains Antivirus version 19.5.4444.567 or earlier is affected.

To safeguard your upgrade experience, we have applied a hold on devices with affected Avast and AVG Antivirus from being offered or installing Windows 10, version 1903 or Windows 10, version 1909, until the application is updated."

Avast and AVG have also released support bulletins [Avast, AVG] with similar information as the one published by Microsoft.

"As of November 2019, AVG Antivirus program versions 19.5 or lower are no longer compatible with the Windows 10, version 1903 (the May 2019 Update). Before your PC can update to this Windows 10 version, a setup dialog displays the applications that need your attention first. If AVG Antivirus appears in this dialog, refer to the relevant instructions below to get the latest version of AVG Antivirus before updating your Windows 10."

When attempting to upgrade with older versions installed, Windows 10 Setup will display a message stating that the user must "Uninstall this app now because it isn't compatible with Windows 10."

This affects AVG Antivirus FREE, AVG Internet Security, Avast Free Antivirus, Avast Pro Antivirus, Avast Internet Security, and Avast Premier.

After updating to the latest version of AVG or Avast Antivirus software, users can then upgrade to either Windows 10 1903 or Windows 10 1909. For most users, I would recommend upgrading to Windows 10 1909 as it is almost like a service pack to 1903 and contains numerous bug fixes.

This is not the first time Microsoft has place compatbility holds on AVG or Avast version, as people have reported [1, 2] similar block as far back as August 2019.

The rest is here:
Windows 10 Upgrades Blocked if Using Old Versions of AVG, Avast - BleepingComputer