Mask and blendshapes refuse to animate ingame

I have built my second avatar now, and just like the previous one, it contains extra bones attached to the humanoid bones which are added into the mask upon importing animations, all preview windows show everything functioning as expected, but once ingame the extra bones and blendshapes do not function or animate at all.

im thinking it might be related to this error message in the builder page telling me certain bones are not “first child” of parent bones, may result in improper targeting or something something.

why not try using constraints or fixed joint to move it?

Is there a tutorial for this?

Idk if there’s a tutorial specifc for that but you can search how constraints work and that will give you an idea.

In general, you should use some Rotation Constraints in your “fake” arm bones that are connected to the real arm bones, that way they will inherit their rotation

edit: just noticed this is 18 days old, hope at least helps someone in the future