No UART Connection via Headers with BX310x

Hi together,

we can not get a UART connection to our BX310x board via the header pins (jumper is set correctly). Tryed to connect with a PC terminal and with an Arduino, both unsuccessful. After pushing the board’s reset button, we do receive a text from the board which says ‘READY’ in the end, but it is not responding to AT commands.

Tried it with and without flow control and at different baud rates.

For any reason it does work via USB. There the board is reacting to AT commands.

Any ideas what could went wrong? Or how to fix it?