Not getting handshake from my client machine

I have used my home wifi connection for testing to crack password. so that ,

I have one Ubuntu machine which is capable of monitoring airodump program. I have used another windows machine act as like client. but i didn't get WPA handshake after running airreply-ng program Also , I have tried to reconnect manually to wifi network from windows client , still not getting handshake. Unfortunately , when i tried to connect my wifi by Ubuntu machine which is monitoring the network, I got the handshake which i can able to crack my password. so , I am wonder why it's not recording the handshake from my other client system . i am still confusing :(

Hope you have understand my problem.

Any helps is much appreciated :)