About a week ago, Microsoft put a hold on v1909 update for users running old Realtek drivers because of compatibility issues. The hold was later lifted as the issue was resolved but now Microsoft has updated their v1909 status page (via Techdows) to confirm a hold on PCs with old AVG and Avast antivirus.
According to the support article, Windows 10 users with old versions of AVG and Avast antivirus won’t be receiving v1909 update. Avast users can check out the support article to find instructions on how to update to a new version of the antivirus. AVG has also published a support article detailing the issue and how users can update to a new version of antivirus.
Microsoft has also advised against forcing the update as that might break Windows and cause further complications. If you’re someone who’s using old Avast or AVG antivirus then make sure to check the support articles or uninstall the antivirus to get the new Windows update.