Every time I install or repair SketchUp the completion dialog says Launch SketchUp, so I would click the Finish button and be disappointed that SketchUp would not start.
This time I decided to hover over the central SketchUp icon and something possessed me to do a left click – and Lo!
When you hover over that SketchUp icon – the cursor should change to the hand cursor (maybe it did and I didn’t notice it).