https://wccftech.com/fix-windows-10-gsod-anti-cheat/

Microsoft has made the May 2019 Update available for everyone who is interested in using the new version through the Release Preview ring. However, some users reported seeing a “This PC can’t be upgraded” alert when trying to install version 1903 on their machines. They also confirmed that they were able to upgrade to the new version after they removed games that use the anti-cheat software.

Version 1903 has been experiencing issues with these games for quite some time now and while Microsoft had earlier said that the issue has been resolved by game makers delivering fixes, the problem still shows up for some users.