Can't hear anyone, and acn't hear me

[urielp]

Hello,

I'm using Zoom on my PC, while I'm the host.

Now, every time, I'm doing test to my microphone and my speakers, and make sure everyting is OK.

In some cases, while other participants are joining the zoom meeting they cannot hear me.

In other cases, I can't hear them as well.

I am doing audio testing (again) and everything is working (I can hear the example sound, and I can hear myself in the microphone test).

What is the issue?

I tried to replace my speakers / microphone etc., but nothing helps...

Thanks,

Uriel