https://www.bleepingcomputer.com/news/microsoft/microsoft-removes-three-windows-10-1903-upgrade-blocks/

Microsoft removed three Windows 10 version 1903 upgrade blocks today after resolving the three critical issues impacting the Windows devices blocked from updating.

According to the Windows Release Health Dashboard the first issue fixed by Microsoft was triggering loss of functionality in the Dynabook Smartphone Link app after installing the Windows 10 May 2019 Update.