Hi Paul,
Make sure that you have the latest firmware in the camera. ONVIF can be problematic sometimes.
Under the ONVIF tab you get Field 1 filled out?, Enter correct logins in field 2, but then Filed 3 do not show up?
Of cause you are sure about username and password?
You don’t give me the models, but you can try to add them under the tab for Custom URL.
Set stream type tu rtsp_tcp or rtsp_udp
Address:
rtsp://username:password@cameraIP:554/live/ch1
or use live/ch0
ch0 or ch1 will probably give you different resolutions.