Hello there.
In VLC take a look at Tools > Codec info. Is there two sets of audio and video info? That indicates that UDP ports are blocked or not mapped properly. VLC is able to failover from UDP to TCP, and that is why you see two audio and two video blocks in that case. However many Android and other devices use UDP and are not able to failover.
What player are you testing playback in? What are the codec details of the stream?
Make sure you are following this guide:
How to re-stream video from an IP camera (RTSP/RTP re-streaming)
If following the above guide, you would need to use a stream name like “camera.stream” in your playback URL.
Lastly you can review the troubleshooting guide:
How to troubleshoot RTSP/RTP playback
Regards,
Salvadore