UI Mask doesnt work with Screen Space - Camera canvas?

Yeah so i was trying to use the ui mask for my hud to realize a nice boss health bar. so i put it all together and it worked in the scene view.
then i tested ingame and it does not work. it doesnt mask its contents. not at all.
so i switched it to screen space- overlay and it worked again. but it doesnt work with screen space - camera. can somebody confirm this? is it a bug? it also doesnt work with worldspace mode. do i have to setup something in order for it to work?

I know this is an old issue but I believe I have found the solution for others that find this page. I was trying to use a mask in the screen space - camera, but certain UI elements would not conform to the mask, exiting its bounds while still being visible. In order to fix this I changed out my masks for 2DRectMask components and they worked as normal.

Hope this helps.

7 views? is that all you got? ugh