Make sure that you are H264 without any other letters or the codec on. Match FPS and iframes.
You need to select Manual IP camera and then your RTSP stream. If you are using a Dahua, it is:
rtsp:/ /user: password@IPADDDRESS:554/cam/realmonitor?channel=1&subtype=1
And there isn't a space between : and password or between the two / but if I put them together it gets this LOL

assword
You need to type that in, wait a moment, then hit test. You may need to hit test two or three times before Rekor finds it.
If it still doesn't like it, then make sure user and password are correct and that they do not contain any special characters.