Participants cant hear each other in break out rooms but can, in main room. Any Pointers??

Hello ZOOMERS,

We are having this issue and no idea how to go about it. Few colleagues have complained that when they add participants of a meeting to a break out room, the participants cannot hear each other but when they are back in the main room, then they do hear each other... I have never encountered this type of issue before... any help will be appreciated.

Steps I have adviced colleagues so far: 
1. s to tell participants to make sure they are using the latest version of the app.
2. To make sure they have a stbale internet connection
3. to ensure they have the right audio settings

Colleagues uses Dell windows with zoom version 5.17.29
thanks