Weird problems to communicate with ATC

I use a Logitech G-430 headphone  ( with an attached mic ) to communicate with ATC via squawk box.( Windows 7 )

For whatever reason I cannot make it work.

I calibrated the mic,turned out ok
I can hear what ATIS says,I can hear what the control tower says to pilots.

But: I sent a voice message to the tower which they did not hear ( had it confirmed by text message )
I then asked the tower ( via text ) to send me a voice message.Result: I could not hear it.

I tried since several days to find a solution,without success.

Could anyone suggest what to do ?

Very much appreicated

Hubert Werni