When you installed SketchUp/LayOut 2019, did you right click on the installer and choose Run as administrator? If not or you aren't sure, quit out of both SketchUp and LayOut, find the installer (Downloads folder?) right click on it and choose Run as administrator from the Context menu. Then when presented with the option, choose Repair. Make sure you have logged into Windows under your normal user, not as the system administrator.
@unknownuser said:
Also, is there some quick way to migrate my workspace from 2018 to 2019, so I don't have to position every icon manually?
Unfortunately not at this time. It is a feature that has been requested, though. Perhaps in an upcoming version we'll see it.
When I get ready to migrate to a new version (I've done it 19 times and on multiple computers) I make screen shots of the entire workspace of the previous version for both SketchUp and LayOut so I can see where all the toolbars are located. Then I import the screen shot into the new version so I can refer to it while setting up the new version.
As Juju implied, do not copy extensions from a previous version into your new version. Install them fresh from their sources.