Try going to C:\Users\<user>\AppData\Roaming\SketchUp\SketchUp 2021\SketchUp\Plugins where <user> is your user name and deleting the openstudio folder and openstudio.rb file. Does that allow SketchUp to start? If so you can try re-installing the OpenStudio SketchUp Plug-in from https://github.com/openstudiocoalition/openstudio-sketchup-plugin/releases or using the SketchUp Extension Warehouse.