Hi Sumit
none of the steps mentioned above in your solving methods have worked to solve my issue with Cumulative update - May 2020. I am running windows 10 pro x64 base system version 1909 . I had all other cumulative updates installed successfully except this one of May 2020 (KB4556799) - Error 0x800f0900. For the last 2 weeks I have followed most of the methods published to solve the May 2020 cumulative update issue but did not work at all!!!
I am puzzled with what happened to have this issue soooo complicated to be solved! And who's fault is it, because my computer windows update system worked perfectly with all other cumulative updates then suddenly stopped working for this specific update. Why Microsoft windows is unable solving this issue automatically ? I appreciate if you have other method that stops this issue.
Thanks
Albert