I can't add or subtract weight paint from some parts of the mesh I have this problem where weight paint is applied to the wrong vertices on my character mesh, for example, the left thigh bone has weight mainly on the right thigh area and the left arm but hardly has any on the left thigh area where it should. When I try to add or subtract from the right thigh nothing happens (but I can add to and subtract from the left arm)



As you can see the left thigh (which is selected) is completely blue ---I figure it should have been mostly red and everything else should have been blue

This is the blend file save, hope it works

https://www.mediafire.com/file/355jizou7ib54c9/male_character_1.blend/file
Just tried your scene: apply the mirror modifier on the mesh so the right leg becomes 'actual' geometry...
Cheers!