RainbowLink 4-channel USB to Serial Converter (RS485 / RS232 / TTL)

"When I connect the TTL port of the 'RainbowLink 4-channel USB to Serial Converter (RS485 / RS232 / TTL)' to an Arduino board (bluepill-stm32f103) via serial, the Arduino IDE recognizes the port but communication does not work. However, with a regular terminal program, communication with the Arduino board works fine. What could be the problem?"