Here's what happened - with comments
1) I downloaded the update which took quite a while. The temporary file was NOT saved, which it should have been.
2) I selected the update now option. Movie Studio 17 closed and then nothing happened. I finally decided that the update was done and reopened Movie Studio 17.
3) A few minutes later I finally received the prompt on my computer to allow Vegas to make changes to my computer, I selected Yes.
4) The update started and then shut down, telling me it could not update with Studio open.
5) I closed Studio, and checked my download files hoping for the temporary file. which was not there.
6) I started the lengthy update process again, and made breakfast, and ate it, while I waited on the download.
7) When I selected the update now option I received the following error. Windows cannot find 'c:\Users.......\17.0\VMSPEUpdate.exe' Make sure you typed the name correctly, and then try again.