RTPS via UART without RTS/CTS not working

After using FastRTPS sucesfully with a Pixhawk 4 mini and RPi, we were looking to use it on a KakuteF7 as well.
We cannot use the USB port, so we use the UART ports. KakuteF7 does not have the RTS/CTS pins, but the documentation states that these shouldn’t be necessary. However, we are not able to create a connection with this one.
If we try to connect the Pixhawk 4 mini without the RTS/CTS pins, it also doesn’t work. It seems strange because I cannot find anywhere that it is required, but still it doesn’t work.
Does anyone have an idea why this might be the case?
Kind regards

It seems like maybe it is not the RTS/CTS that is causing the issue. I am still not able to connect the micrortps_bridge on the KakuteF7 however…