Some Windows 10 users are being blocked from applying the May 2020 Update due to unsupported settings on Windows 10 2004. Users advised to update drivers, disable Core Isolation to have May 2020 update offered through Windows Update. Microsoft hasn’t officially acknowledged this issue and no official solution is yet available. Unofficial fix shared by one user on Microsoft’s TechNet web portal for IT professionals that has been confirmed to work. Users can follow this guided walk-through or make use of this Windows 10 update problems troubleshooter.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-2004-upgrades-blocked-by-useless-what-needs-your-attention-alerts/