Call of Duty Warzone Crossplay you can't hear PC players?

Moin, I (PS4) wanted to play Warzone together with a friend (PC) yesterday. The problem is that you can't hear him and he can't hear me.

His headset works everywhere else on the PC (Discord, other games, etc.). He has also activated crossplay and voice chat is activated in the settings, so we have already checked the usual suspects. Likewise, all videos on Youtube on the topic.

Does anyone have any idea what the problem is?

The funny thing is that the day before I was playing with another buddy who also plays on the PC, and everything worked out for him regarding voice chat.

Is the voice chat set to the open microphone?

Or is his microphone even recognized in the game?

It was definitely set to "Open Micro". But it was probably not recognized by the game.

In the settings there's the possibility to test the microphone

If it already fails, it is clear that you can't hear each other.

Either it is due to the sound settings in Windows or the microphone is not approved for Warzone

Thanks in advance! I'll pass it on, I think we will unfortunately only get to test it tonight.

But the problem must lie with Him. You can't recognize the speaker symbol next to his name in-game, even if he has connected it SECURELY.

How could you find out if the mic is not approved for Warzone? Sorry for the maybe stupid question.

In the microphone privacy settings

Tried and did not work, everything is set correctly.

So with the Battle.net Launcher the headset works, so the mic test fails. In-game it is so that it doesn't work.