one-off audio problem

I have Zoom meetings with several groups where I can hear and be heard fine.  Some are on an iPad and some are on a Windows 10 desktop computer.  My friend has Zoom meetings where she can hear an be heard fine using a Windows laptop.  When she and I try to have a Zoom meeting I can hear her but she cannot hear me.  This has happened twice several weeks apart.  Suggestions welcome.  Thanks.