How can I use the apple headset to speak on fortnite on the ipad?

I play on the ipad fortnite and as a headset I have the apple headset (cable inear)…

Sound works, but I can't speak?!

In the settings at fortnite I have voice chat on - push-to-talk on / off tried both without success… Volume is everywhere even at 100 …

Headset plugged in via jack or lightning…

Does that work with an Apple headset?

Usually it should work. Do you have any other headphones that you can test? If all of them don't work, it's somehow the computer