Problems with UART (flow control) on max32630fthr

I tried multiple version of mbed-os from 5.15 to 6.16, but I can not get the flow control (RTS/CTS) to work on UART2.

Does anyone know if it is MAX32630FTHR board problem (hardware / layout) or a software problem (poor maxim support / …)?
Does the code require to call some other “initialization” functions? (Doesn’t matter if I use unbuffered or buffered serial, both not working.)
UnbufferedSerial s(UART2_TX, UART2_RX, 115200);
s.set_flow_control(SerialBase::RTSCTS, UART2_RTS, UART2_CTS);
// s.write(…); …

(I’m using correct pins on the max32 board), connections between devices are:
TX - RX
RX - TX
RTS - CTS
CTS - RTS

I also can not get faster baud rate than 115200, but for now the flow control is the biggest issue for me.

Thanks for any advice or solution.