Blender 2.93 problem with hair particle sistem within group

f i create a group of vertices for hair particle density nothing happens, here the video

i do something wrong?

Have you scaled the model?
Do you have any modifiers? → Try checking “use modifer Stack” in Partical system settings > Emmission > Source. Or if that does not solve it, maybe appling helps?

it actually shows one single hair! probably is bugged

have you checked what happens when you select " Use modifier stack"? ( see your screen shot)

thank you tachtian, i guess i’ve to weight the group to make it grow hair, now i understand!