Some have found that by restoring to before the TH2 update and then a manual check for updates got the update installed.
Others have had to resort to using the Media Creation Tool which includes TH2 now, but I did see a warning about using that on an existing Win 10, but can't remember what it was and MS seemed to have pulled the website with the Upgrade Now button that would give you it.
Edit - Just remembered what the warning is.
When used on an existing Win 10 it can overwrite temporary files that are needed if you ever wanted to revert to your previous Windows version - but if you are past that stage then that would be academic.