Microsoft removed two Windows 10 version 1903 upgrade blocks after resolving known issues behind them. Microsoft resolved six known issues in the KB4512941 optional cumulative update released on August 30. The two known issues were added to the Windows Release Health Dashboard on July 25. Users should note that, in some cases, it may take up to 48 hours until the Windows 10 May 2019 Update can be installed on their devices. Users can troubleshoot update problems using the info available in this support article or go through this guided walk-through.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-removes-two-windows-10-1903-upgrade-blocks/