When you say your "account is admin", do you mean your normal Windows user account has admin powers ?
That's not the same as running SketchUp while logged into the administrator account, which is a different animal ! and should be avoided...
And of course, while logged-in as your normal account you need to do the right-click on the installer's exe and 'Run as administrator'.
Otherwise the files/folders installed by SketchUp for its own use, and for your use as 'user' will get unexpected permissions and cause issues...
Assuming that your error message is much the same as previously reported - albeit for v2018, when you quote v2019 ? - then something is preventing SketchUp from copying its 'Shipped' extensions from its main Program Files folder to your user Plugins folder in the AppData path...