FlexSim currently supports importing SketchUp 2019 models.
On SketchUp 3D warehouse (https://3dwarehouse.sketchup.com/), you can easily download a SketchUp 2019 model:
And then import it directly in FlexSim.
In January 2022, SketchUp 2022 will be released. It's very likely that SketchUp 2019 format will be removed from the download pickoptions in the 3D warehouse. This means that FlexSim users will not be able to directly import a SketchUp file downloaded from the 3D warehouse. They will need to open the file in SketchUp, and then export it to an older SketchUp version or another format. As far as I know, this is not possible in SketchUp free, it requires a license or a subscription.
If you want that FlexSim updates the SketchUp importer, please vote for this idea.