This is most perplexing.
Earlier versions of SketchUp/Ruby would fail on PCs with accented names in paths.
This occurred in many extensions/plugins...
So it was always recommended to use SketchUp while logged into Windows with a non-accented name.
But in the newer SketchUp/Ruby versions there are tools to force the string's encoding into UTF-8...
This has been tested and works most of the time.
However, as in your case, sometimes it fails.
There can be multiple reasons - the encode used by Windows itself etc - Win-1252 v. UTF-8 v. ANSI v. Unicode...
However, I'm unclear what your settings might be and what they could become...
Unfortunately you can't simply rename your User login.
Although it'll appear without the accent the path to which it refers retains its origin name - with the accent.
One work around is to make a brand new admin User in Windows named 'Sean' rather than 'Seán'.
Also make another admin user named 'Temp' - you need to use that login as you can't copy/paste files for an active user...
Then copy your entire Windows set up to that user's folders.
Then use that new login... and delete the old one later...
However, it's no simple feat...
Check here on guidance - there's a lot to copy...http://www.thewindowsclub.com/share-tra ... ts-windowshttps://support.microsoft.com/en-us/hel ... =windows-7
Most folks interested in recovering/copying a profile are interested in the contents of ....
And their AppData folder (Hidden by default)
Normally it's suggested that people recover what they are truly interested in and leave anything labeled ntuser or NTUSER as those files may be accountable for the profile corruption in the first place.
Of course, depending on the circumstances there may be other means and methods of recovering from a corrupt user profile.
If there is a specific error message then perhaps searching for that might prove more beneficial.