Can you let us know the resolution,byte per pixel and frame rate of the video you are streaming. Is the data streaming rate (resolution*frame rate*byte per pixel) greater than 2.4 Gbps?
The maximum data rate supported by CX3 is 2.4 Gbps. If you are streaming higher than this data rate, you need to use a FPGA in between to provide buffering and throttle the data rate.
Can you please attach the MIPI CSI configuration tool screenshot here? The video data may not stream if the MIPI bridge configuration is incorrect. Are you seeing any MIPI related error?