Microsoft has placed a compatibility hold on devices with older versions of the BattlEye anti-cheat software. This means that the Windows 10, version 1903 update won’t be offered to those PCs until the incompatible version of Battleye is removed or replaced. An update has already been released and been provided to game developers for known games that are affected by this issue, but unless you upgrade your games, you will not receive the fix. Microsoft recommends the following steps if you are unable to upgrade to Windows 10 version 1903.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-1903-being-blocked-if-using-older-battleye-software/