There’s a great standalone tool that you can use to help troubleshoot Windows 10 upgrade issues. This tool only works on Windows 10 with .Net Framework 4.6 installed. You can download the tool from here.
Setupdiag.exe is a command line tool that parses all of the log files associated with windows upgrades and looks for known failure signatures. Simply running the command on a windows 10 system will page up all of the log files into a zip file in the directory from which the command was run.
There are many command line switches (some for controlling output destinations) and as usual you can get a list of the options by typing SetupDiag.exe /?.
Here are some examples of the output from SeupDiag.exe on a system that had a successful upgrade:
Note that I use the Configuration Manager Trace Log Tool as my default log file viewer. More on the setupdiage.exe can be found here.