I apologize, the way I wrote that was unclear! The outside quotes are important to include in this case. So what you enter into PS should be this, including all quotes: "C:\Program Files\R\R-4.1.0\bin\Rscript.exe" -e "tempdir()"
Were you able to check if you have access to C:\Users\{your-user-name}\AppData\Local\Temp?