For those of you having problems installing the New Windows 10 May 2004 Update. This Link will take you to a MS Document that lists some of the known issues with the update.
https://docs.microsoft.com/en-us/windows/release-information/status-windows-10-2004
I used the "Media Creation Tool" to install the update, and had NO problems. I do not recommend the Update Assistant at his time. If you still see problems I recommend for you to wait awhile till you update.
I Hope This Helps Some of you.
I have chat with windows advisory and he said use win 10 assistant tool to upgrade if you can not see the may update in win may 2020 update. but you are advice to install fresh win may2020 update. so still I have confusion a lot. I have always face problem to upgrade a new version of win 10 normally update has to enhance the operating system but in windows it always a difficult to update.