The masks for parts of the body will be created by using Quick Actions > Retouch. The Retouch feature creates masks when aditing eyes, teeth, hair, clothing, etc.
Hi @??????_??????9429, Can you share a bit more information about the issue you're seeing? Some screenshots and/or a screen recording would be very helpful. Also, let us know which version of Lightroom and OS you're working with. Thanks! ^CH