When a participant asks for help, the meeting host will be notified and prompted to join the relevant breakout room.

To request assistance while in a breakout room, click the Breakout rooms icon (this will be in the More menu if it is not already on the toolbar) and select Ask for Help.  

A screenshot of the Zoom meeting controls toolbar.

When prompted, confirm your request by clicking Invite Host

A screenshot of a Zoom meeting pop-up in which the participant is being prompted to Invite the host to their breakout room.

The pop-up will inform you that the meeting host has been notified and prompted to join your room.

A screenshot of a Zoom meeting pop-up in which the participant is being informed that the host has been invited to their breakout room.