Communication Problems Xbox wireless headset - Halo 5 Coop

Hi,

My son and I have an issue hearing / talking to eachother in Halo 5 Coop.

2 - seperate copies of Halo 5.

My Setup:

• Xbox Wireless Headset
  
• Xbox Series X - wired connection to the modem
  

My Sons Setup:

• Xbox Wireless Headset
  
• Xbox One - Wifi
  

In the game my son is able to hear me but I am not able to hear him. Software update on both headsets have been done. What are we doing wrong and why am I not able to hear my son.

:)