https://support.microsoft.com/en-us/topic/description-of-the-security-update-for-microsoft-exchange-server-2019-2016-and-2013-march-2-2021-kb5000871-9800a6bb-0a21-4ee7-b9da-fa85b3e1d23b

1. Update fails to stop all services ( do this manually ) 

2. Exchange services might remain in a disabled state after you install this security update. This condition does not indicate that the update is not installed correctly. This condition might occur if the service control scripts experience a problem when they try to return Exchange services to their usual state.
   
   To fix this issue, use Services Manager to restore the startup type to Automatic, and then start the affected Exchange services manually. To avoid this issue, run the security update at an elevated command prompt. For more information about how to open an elevated Command Prompt window, see Start a Command Prompt as an Administrator.