Assuming all of the previously mentioned ‘prerequisites’ have been met without success…
You original post mentions ‘administrator’ - and is at best ambiguous.
For the avoidance of doubt, SketchUp must be installed properly to avoid unpredictable issues with file/folder permissions etc…
Even if you [as your normal Windows-user] have admin-powers, OR are even the main system administrator [not normally recommended], the only proper way to install [or repair] SketchUp is as follows.
Log in as your normal Windows user-account.
If SketchUp is open then close it.
Find the SketchUp installer’s exe file [probably in your Downloads folder ?]
Select its icon, right-click > context-menu > “Run as administrator”…
When prompted choose “Repair” [this should not adversely affect custom settings or plugins etc].
Note that if that still doesn’t work choose “Uninstall”, then immediately after that competes repeat, choosing “Install”.
Note that for a fresh installation requires you to choose “Install”.
When it completes try restarting SketchUp…
On newer PCs installing any complex app like SketchUp must be done using “Run as administrator”.
Doing it any other way causes unpredictable issues.
Never double-click the installer’s exe file’s icon to Run it - it is not equivalent to doing it properly - even if you have admin-powers !