https://www.bleepingcomputer.com/news/microsoft/windows-10-2004-update-not-offered-heres-how-to-get-it-now/

Microsoft officially started rolling out Windows 10 version 2004, the Windows 10 May 2020 Update yesterday, but for many people, it is not being offered when they check via Windows Update.

If you are performing a manual Windows Update check and it just states "You're up to date," as seen below, then you have not been selected yet as part of the initial rollout.